KERNAL is Commodore 's name for the ROM -resident operating system core in its 8-bit home computers ; from the original PET of 1977, followed by the extended but related versions used in its successors: the VIC-20 , Commodore 64 , Plus/4 , Commodore 16 , and Commodore 128 .
127-692: The Commodore 8-bit machines' KERNAL consists of the low-level, close-to-the-hardware OS routines roughly equivalent to the BIOS in IBM PC compatibles (in contrast to the BASIC interpreter routines, also located in ROM) as well as higher-level, device-independent I/O functionality. It is user-callable via a jump table in RAM whose central (oldest) part, for reasons of backwards compatibility , remains largely identical throughout
254-404: A PRINT CHR$ ( X ) command where X corresponds to the control code to be issued (for example, PRINT CHR$ ( 147 ) is the control code to clear the screen) or by pressing the key in question between quote marks, thus pressing ⇧ Shift + CLR HOME following a quote mark will cause BASIC to display the visual representation of the control code (in this case, a reversed heart) which
381-519: A REM (BASIC statement to add a comment to the code) followed by a {Shift-L} , when trying to view the program listing, the BASIC interpreter would immediately abort the listing, display a ?SYNTAX ERROR and return to the READY. prompt. This glitch was used to some effect by programmers who wanted to try and protect their work, although it was fairly easy to circumvent. By abbreviating keywords, it
508-519: A network adapter attempts booting by a procedure that is defined by its option ROM or the equivalent integrated into the motherboard BIOS ROM. As such, option ROMs may also influence or supplant the boot process defined by the motherboard BIOS ROM. With the El Torito optical media boot standard , the optical drive actually emulates a 3.5" high-density floppy disk to the BIOS for boot purposes. Reading
635-533: A BIOS upgrade that fails could brick the motherboard. Unified Extensible Firmware Interface (UEFI) is a successor to the legacy PC BIOS, aiming to address its technical limitations. UEFI firmware may include legacy BIOS compatibility to maintain compatibility with operating systems and option cards that do not support UEFI native operation. Since 2020, all PCs for Intel platforms no longer support Legacy BIOS. The last version of Microsoft Windows to officially support running on PCs which use legacy BIOS firmware
762-475: A PET was by modifying the first two bytes with a disk sector editor as the CBM-II series had their BASIC program area at $ 0, which would result in a PET attempting to load into the zero page and locking up. Commodore BASIC keywords could be abbreviated by entering first an unshifted keypress, and then a shifted keypress of the next letter. This set the high bit , causing the interpreter to stop reading and parse
889-602: A ROM chip) that contains a BIOS extension ROM. The motherboard BIOS typically contains code for initializing and bootstrapping integrated display and integrated storage. The initialization process can involve the execution of code related to the device being initialized, for locating the device, verifying the type of device, then establishing base registers, setting pointers , establishing interrupt vector tables, selecting paging modes which are ways for organizing available registers in devices, setting default values for accessing software routines related to interrupts , and setting
1016-523: A SLIC can be preactivated with an OEM product key, and they verify an XML formatted OEM certificate against the SLIC in the BIOS as a means of self-activating (see System Locked Preinstallation , SLP). If a user performs a fresh install of Windows, they will need to have possession of both the OEM key (either SLP or COA) and the digital certificate for their SLIC in order to bypass activation. This can be achieved if
1143-453: A backwards jump, they will return to the start of the program to begin searching. This will slow down larger programs, so it is preferable to put commonly used subroutines near the start of a program. Variable names are only significant to 2 characters; thus the variable names VARIABLE1 , VARIABLE2 , and VA all refer to the same variable. Commodore BASIC also supports bitwise operators — AND, OR , and XOR , although this feature
1270-414: A game or when waiting for user input, programmers could poll by reading selected memory locations (such as $ C6 for the 64, or $ D0 for the 128, denoting size of the keyboard queue) to delay or halt execution. A unique feature of Commodore BASIC is the use of control codes to perform tasks such as clearing the screen or positioning the cursor within a program; these can be invoked either by issuing
1397-608: A hard disk that is bootable, but sometimes there is a removable-media drive that has higher boot priority, so the user can cause a removable disk to be booted. In most modern BIOSes, the boot priority order can be configured by the user. In older BIOSes, limited boot priority options are selectable; in the earliest BIOSes, a fixed priority scheme was implemented, with floppy disk drives first, fixed disks (i.e., hard disks) second, and typically no other boot devices supported, subject to modification of these rules by installed option ROMs. The BIOS in an early PC also usually would only boot from
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#17327722232851524-478: A host of bad programming traps for the programmer. As most of these issues derived from Microsoft BASIC , virtually every home computer BASIC of the era suffered from similar deficiencies. Every line of a Microsoft BASIC program was assigned a line number by the programmer. It was common practice to increment numbers by some value (5, 10 or 100) to make inserting lines during program editing or debugging easier, but bad planning meant that inserting large sections into
1651-572: A jump table was new to small computers then. The Adventure International games published for the VIC-20 on the cartridge are an example of software that uses the KERNAL. Because they only use the jump table, the games can be memory dumped to disk, loaded into a Commodore 64, and run without modification. The KERNAL was initially written for the Commodore PET by John Feagans, who introduced
1778-561: A message like "No bootable disk found"; some would prompt for a disk to be inserted and a key to be pressed to retry the boot process. A modern BIOS may display nothing or may automatically enter the BIOS configuration utility when the boot process fails. The environment for the boot program is very simple: the CPU is in real mode and the general-purpose and segment registers are undefined, except SS, SP, CS, and DL. CS:IP always points to physical address 0x07C00 . What values CS and IP actually have
1905-451: A minute in BASIC. To execute faster than the interpreter, programmers started using various techniques to speed up execution. One was to store often-used floating point values in variables rather than using literal values, as interpreting a variable name was faster than interpreting a literal number. Since floating point is default type for all commands, it's faster to use floating point numbers as arguments, rather than integers. When speed
2032-444: A momentary delay in program execution if a large array is dimensioned. String variables are represented by tagging the variable name with a dollar sign. Thus, the variables AA$ , AA , and AA% would each be understood as distinct. Array variables are also considered distinct from simple variables, thus A and A(1) do not refer to the same variable. The size of a string array merely refers to how many strings are stored in
2159-547: A network device or a SCSI adapter) in a cooperative way, it can use the BIOS Boot Specification (BBS) API to register its ability to do so. Once the expansion ROMs have registered using the BBS APIs, the user can select among the available boot options from within the BIOS's user interface. This is why most BBS compliant PC BIOS implementations will not allow the user to enter the BIOS's user interface until
2286-420: A nuisance to edit. The LIST command displayed the entire command keyword - extending the program line beyond the 2 or 4 screen lines which could be entered into program memory. Like the original Microsoft BASIC interpreter , Commodore BASIC is slower than native machine code . Test results have shown that copying 16 kilobytes from ROM to RAM takes less than a second in machine code, compared to over
2413-598: A number of commands for graphics and sound support on the C16 and Plus/4 . BASIC 7.0 was included with the Commodore 128 , and included structured programming commands from the Plus/4's BASIC 3.5, as well as keywords designed specifically to take advantage of the machine's new capabilities. A sprite editor and machine language monitor were added. The last, BASIC 10.0, was part of the unreleased Commodore 65 . Commodore took
2540-480: A number of disk-related commands, including the ability to read a disk directory without destroying the program in memory. Its features were subsequently incorporated in various third-party extensions, such as the popular Epyx FastLoad cartridge. Other BASIC extensions added additional keywords to make it easier to code sprites, sound, and high-resolution graphics like Simons' BASIC (1983) and Vision BASIC (2022). Although BASIC 2.0's lack of sound or graphics features
2667-400: A one digit number. The order of execution of Commodore BASIC lines was not determined by line numbering; instead, it followed the order in which the lines were linked in memory. Program lines were stored in memory as a singly linked list with a pointer (containing the address of the beginning of the next program line), a line number, and then the tokenized code for the line. While a program
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#17327722232852794-565: A percent sign) in the range -32768 to 32767, in practice they are only used for array variables and serve the function of conserving memory by limiting array elements to two bytes each (an array of 2000 elements will occupy 10,000 bytes if declared as a floating point array, but only 4000 if declared as an integer array). Denoting any variable as integer simply causes BASIC to convert it back to floating point, slowing down program execution and wasting memory as each percent sign takes one additional byte to store (since this also applies to integer arrays,
2921-503: A perpetual license. The original PET version was very similar to the original Microsoft implementation with few modifications. BASIC 2.0 on the C64 was also similar, and was also seen on C128s (in C64 mode) and other models. Later PETs featured BASIC 4.0, similar to the original but adding a number of commands for working with floppy disks . BASIC 3.5 was the first to really deviate, adding
3048-422: A portion of the " upper memory area " (the part of the x86 real-mode address space at and above address 0xA0000) and runs each ROM found, in order. To discover memory-mapped option ROMs, a BIOS implementation scans the real-mode address space from 0x0C0000 to 0x0F0000 on 2 KB (2,048 bytes) boundaries, looking for a two-byte ROM signature : 0x55 followed by 0xAA. In a valid expansion ROM, this signature
3175-504: A program often required restructuring the entire code. A common technique was to start a program at some low line number with an ON...GOSUB jump table , with the body of the program structured into sections starting at a designated line number like 1000, 2000, and so on. If a large section needed to be added, it could just be assigned the next available major line number and inserted to the jump table. In addition, all variables are treated as global variables. Clearly defined loops beyond
3302-468: A relocatable binary image. Thus, the burden of collisions both in I/O space and in memory space falls upon the user, while platform compatibility across a wide range of machines falls upon the software author. Nonetheless, support software for these functions could easily be implemented if desired. Logical filename formats tends to depend upon the specific device addressed. The most common device used, of course,
3429-464: A reserved block of system RAM at addresses 0x00400–0x004FF with various parameters initialized during the POST. All memory at and above address 0x00500 can be used by the boot program; it may even overwrite itself. The BIOS ROM is customized to the particular manufacturer's hardware, allowing low-level services (such as reading a keystroke or writing a sector of data to diskette) to be provided in
3556-529: A selected increment. Earlier BASICs from Commodore also lack debugging commands, meaning that bugs and unused variables are hard to trap. IF...THEN...ELSE structures, a standard part of Z80 Microsoft BASICs, were added to BASIC 3.5 after being unavailable in earlier versions of Commodore BASIC. In common with other home computers , Commodore's machines booted directly into the BASIC interpreter. BASIC's file and programming commands could be entered in direct mode to load and execute software. If program execution
3683-575: A separate EDIT command, or a "copy cursor" that truncated the line at the cursor's position. It also had the capability of saving named files to any device, including the cassette – a popular storage device in the days of the PET, and one that remained in use throughout the lifespan of the 8-bit Commodores as an inexpensive form of mass storage. Most systems only supported filenames on diskette , which made saving multiple files on other devices more difficult. The user of one of these other systems had to note
3810-503: A simple boot loader in its ROM.) Versions of MS-DOS , PC DOS or DR-DOS contain a file called variously " IO.SYS ", " IBMBIO.COM ", "IBMBIO.SYS", or "DRBIOS.SYS"; this file is known as the "DOS BIOS" (also known as the "DOS I/O System") and contains the lower-level hardware-specific part of the operating system. Together with the underlying hardware-specific but operating system-independent "System BIOS", which resides in ROM , it represents
3937-621: A software licensing description table (SLIC), a digital signature placed inside the BIOS by the original equipment manufacturer (OEM), for example Dell . The SLIC is inserted into the ACPI data table and contains no active code. Computer manufacturers that distribute OEM versions of Microsoft Windows and Microsoft application software can use the SLIC to authenticate licensing to the OEM Windows Installation disk and system recovery disc containing Windows software. Systems with
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4064-454: A standardized way to programs, including operating systems. For example, an IBM PC might have either a monochrome or a color display adapter (using different display memory addresses and hardware), but a single, standard, BIOS system call may be invoked to display a character at a specified position on the screen in text mode or graphics mode . The BIOS provides a small library of basic input/output functions to operate peripherals (such as
4191-606: A three-byte mantissa is only about 6.5 decimal digits, and round-off error is common. 6502 implementations of Microsoft BASIC utilized 40-bit floating point arithmetic, meaning that variables took five bytes to store (four byte mantissa and one byte for the exponent) unlike the 32-bit floating point found in BASIC-80. While 8080/Z80 implementations of Microsoft BASIC supported integer and double precision variables, 6502 implementations were floating point only. Although Commodore BASIC supports signed integer variables (denoted with
4318-476: Is Windows 10 as Windows 11 requires a UEFI-compliant system (except for IoT Enterprise editions of Windows 11 since version 24H2 ). The term BIOS (Basic Input/Output System) was created by Gary Kildall and first appeared in the CP/M operating system in 1975, describing the machine-specific part of CP/M loaded during boot time that interfaces directly with the hardware . (A CP/M machine usually has only
4445-544: Is firmware used to provide runtime services for operating systems and programs and to perform hardware initialization during the booting process (power-on startup). The firmware comes pre-installed on the computer's motherboard . The name originates from the Basic Input/Output System used in the CP/M operating system in 1975. The BIOS firmware was originally proprietary to the IBM PC ; it
4572-550: Is a resource name up to 16 characters in length (most characters allowed except for certain special characters), and ATTRS is an optional comma-separated list of attributes or flags. For example, if the user wants to overwrite a program file called PRGFILE , they might see a filename like @0:PRGFILE,P used in conjunction with device 8 or 9. Meanwhile, a filename for the RS-232 driver (device 2) consists simply of four characters, encoded in binary format. Other devices, such as
4699-460: Is assigned two system variables in BASIC, TI and TI$ , which both contain the current time. TI is read-only and cannot be modified; doing so will result in a Syntax Error message. TI$ may be used to set the time via a six number string (an error results from using a string other than six numbers). The clock is not a very reliable method of timekeeping since it stops whenever interrupts are turned off (done by some kernal routines) and accessing
4826-406: Is bootable by attempting to load the first sector ( boot sector ). If the sector cannot be read, the BIOS proceeds to the next device. If the sector is read successfully, some BIOSes will also check for the boot sector signature 0x55 0xAA in the last two bytes of the sector (which is 512 bytes long), before accepting a boot sector and considering the device bootable. When a bootable device is found,
4953-640: Is executed and if there are many string variables and arrays that have been manipulated over the course of a program, clearing them can take more than an hour under the worst conditions. It is also not possible to abort garbage collection as BASIC does not scan the RUN/STOP key while performing this routine. BASIC 4.0 introduced an improved garbage collection system with back pointers and all later implementations of Commodore BASIC also have it. The FRE function in BASIC 2.0 suffered from another technical flaw in that it cannot handle signed numbers over 32768, thus if
5080-452: Is followed by a single byte indicating the number of 512-byte blocks the expansion ROM occupies in real memory, and the next byte is the option ROM's entry point (also known as its "entry offset"). If the ROM has a valid checksum, the BIOS transfers control to the entry address, which in a normal BIOS extension ROM should be the beginning of the extension's initialization routine. At this point,
5207-421: Is found at address $ FFD2 (65490), to send a text string to the default output device (e.g., the display screen). The KERNAL was known as kernel inside of Commodore since the PET days, but in 1980 Robert Russell misspelled the word as kernal in his notebooks. When Commodore technical writers Neil Harris and Andy Finkel collected Russell's notes and used them as the basis for the VIC-20 programmer's manual,
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5334-415: Is not declared with a DIM statement, it is automatically set to ten elements (in practice 11 since array elements are counted from 0). Larger arrays must be declared or BASIC will display an error when the program is run and an array cannot be re-dimensioned in a program unless all variables are wiped via a CLR statement. Numeric arrays are automatically filled with zeros when they are created, there may be
5461-556: Is not well defined. Some BIOSes use a CS:IP of 0x0000:0x7C00 while others may use 0x07C0:0x0000 . Because boot programs are always loaded at this fixed address, there is no need for a boot program to be relocatable. DL may contain the drive number, as used with interrupt 13h , of the boot device. SS:SP points to a valid stack that is presumably large enough to support hardware interrupts, but otherwise SS and SP are undefined. (A stack must be already set up in order for interrupts to be serviced, and interrupts must be enabled in order for
5588-471: Is performed each time the system is powered up. Without reprogrammable microcode, an expensive processor swap would be required; for example, the Pentium FDIV bug became an expensive fiasco for Intel as it required a product recall because the original Pentium processor's defective microcode could not be reprogrammed. Operating systems can update main processor microcode also. Some BIOSes contain
5715-483: Is possible to fit even more on a line. BASIC 7.0 displays a ?STRING TOO LONG error if the user enters a program line over 160 characters in length. Earlier versions do not produced an error and simply display the READY prompt two lines down if the line length is exceeded. The line number is counted in the number of characters in the program line, so a five digit line number will result in four fewer characters allowed than
5842-541: Is rebooting. When interrupt 19h is called, the BIOS attempts to locate boot loader software on a "boot device", such as a hard disk , a floppy disk , CD , or DVD . It loads and executes the first boot software it finds, giving it control of the PC. The BIOS uses the boot devices set in Nonvolatile BIOS memory ( CMOS ), or, in the earliest PCs, DIP switches . The BIOS checks each device in order to see if it
5969-488: Is running. The interrupt vectors corresponding to the BIOS interrupts have been set to point at the appropriate entry points in the BIOS, hardware interrupt vectors for devices initialized by the BIOS have been set to point to the BIOS-provided ISRs, and some other interrupts, including ones that BIOS generates for programs to hook, have been set to a default dummy ISR that immediately returns. The BIOS maintains
6096-401: Is the floppy disk system, which uses a format similar to MD:NAME,ATTRS , where M is a flag of sorts ($ for directory listing, @ for indicating a desire to overwrite a file if it already exists, unused otherwise.), D is the (optional) physical disk unit number (0: or 1: for dual-drive systems, just 0: for single-disk units like the 1541, et al., which defaults to 0: if left unspecified), NAME
6223-512: Is then acted upon at program execution (directly printing out the control codes uses less memory and executes faster than invoking a CHR$ function). This is in comparison to other implementations of BASIC which typically have dedicated commands to clear the screen or move the cursor. BASIC 3.5 and up have proper commands for clearing the screen and moving the cursor. Program lines in Commodore BASIC do not require spaces anywhere (but
6350-663: Is unique among PCs in having two ROM cartridge slots on the front. Cartridges in these slots map into the same region of the upper memory area used for option ROMs, and the cartridges can contain option ROM modules that the BIOS would recognize. The cartridges can also contain other types of ROM modules, such as BASIC programs, that are handled differently. One PCjr cartridge can contain several ROM modules of different types, possibly stored together in one ROM chip. The 8086 and 8088 start at physical address FFFF0h. The 80286 starts at physical address FFFFF0h. The 80386 and later x86 processors start at physical address FFFFFFF0h. When
6477-448: Is used via a fixed 5-byte seed value stored at power on in memory locations $ 8B-$ 8F on the C64 (the location differs on other machines). RND with any number higher than 0 will generate a random number amalgamated from the value included with the RND function and the seed value, which is updated by 1 each time an RND function is executed. RND with a negative number goes to a point in
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#17327722232856604-511: The LIST command will always display one between the line number and the statement), e.g., 100 IF A = 5 THENPRINT "YES" : GOTO 160 , and it was common to write programs with no spacing. This feature was added to conserve memory since the tokenizer never removes any space inserted between keywords: the presence of spaces results in extra 0x20 bytes in the tokenized program which are merely skipped during execution. Spaces between
6731-464: The LOAD command will always load at the first two bytes contained in the program file. This created a problem when trying to load BASIC programs saved on other Commodore machines as they would load at a higher address than where the PET's BASIC expected the program to be, there were workarounds to "move" programs to the proper location. If a program was saved on a CBM-II machine, the only way to load it on
6858-611: The CPU , chipset , RAM , motherboard , video card , keyboard , mouse , hard disk drive , optical disc drive and other hardware , including integrated peripherals . Early IBM PCs had a routine in the POST that would download a program into RAM through the keyboard port and run it. This feature was intended for factory test or diagnostic purposes. After the motherboard BIOS completes its POST, most BIOS versions search for option ROM modules, also called BIOS extension ROMs, and execute them. The motherboard BIOS scans for extension ROMs in
6985-481: The GEOS KERNAL. Surprisingly, the KERNAL implemented a device-independent I/O API not entirely dissimilar from that of Unix or Plan-9 , which nobody actually exploited, as far as is publicly known. Whereas one could reasonably argue that "everything is a file" in these latter systems, others could easily claim that "everything is a GPIB -device" in the former. Due to limitations with the 6502 architecture at
7112-488: The PET (1977) to the Commodore 128 (1985). The core is based on 6502 Microsoft BASIC , and as such it shares many characteristics with other 6502 BASICs of the time, such as Applesoft BASIC . Commodore licensed BASIC from Microsoft in 1977 on a "pay once, no royalties " basis after Jack Tramiel turned down Bill Gates ' offer of a $ 3 per unit fee, stating, "I'm already married," and would pay no more than $ 25,000 for
7239-713: The "command channel" for peripherals, relying on message-passing techniques to communicate both commands and results, including exceptional cases. For example, in Commodore BASIC , they might find software not unlike the following: Device numbers, per established documentation, are restricted to the range [0,16]. However, this limitation came from the specific adaptation of the IEEE-488 protocol and, in effect, applies only to external peripherals. With all relevant KERNAL system calls vectored, programmers can intercept system calls to implement virtual devices with any address in
7366-423: The "first sector" of a CD-ROM or DVD-ROM is not a simply defined operation like it is on a floppy disk or a hard disk. Furthermore, the complexity of the medium makes it difficult to write a useful boot program in one sector. The bootable virtual floppy disk can contain software that provides access to the optical medium in its native format. If an expansion ROM wishes to change the way the system boots (such as from
7493-430: The 1980s under MS-DOS , when programmers observed that using the BIOS video services for graphics display were very slow. To increase the speed of screen output, many programs bypassed the BIOS and programmed the video display hardware directly. Other graphics programmers, particularly but not exclusively in the demoscene , observed that there were technical capabilities of the PC display adapters that were not supported by
7620-424: The BIOS after completing its initialization process. Once (and if) an option ROM returns, the BIOS continues searching for more option ROMs, calling each as it is found, until the entire option ROM area in the memory space has been scanned. It is possible that an option ROM will not return to BIOS, pre-empting the BIOS's boot sequence altogether. After the POST completes and, in a BIOS that supports option ROMs, after
7747-482: The BIOS provided BIOS interrupt calls for the keyboard, display, storage, and other input/output (I/O) devices that standardized an interface to application programs and the operating system. More recent operating systems do not use the BIOS interrupt calls after startup. Most BIOS implementations are specifically designed to work with a particular computer or motherboard model, by interfacing with various devices especially system chipset . Originally, BIOS firmware
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#17327722232857874-601: The BIOS to carry out most input/output tasks within the PC. Calling real mode BIOS services directly is inefficient for protected mode (and long mode ) operating systems. BIOS interrupt calls are not used by modern multitasking operating systems after they initially load. In the 1990s, BIOS provided some protected mode interfaces for Microsoft Windows and Unix-like operating systems, such as Advanced Power Management (APM), Plug and Play BIOS , Desktop Management Interface (DMI), VESA BIOS Extensions (VBE), e820 and MultiProcessor Specification (MPS). Starting from
8001-408: The BIOS transfers control to the loaded sector. The BIOS does not interpret the contents of the boot sector other than to possibly check for the boot sector signature in the last two bytes. Interpretation of data structures like partition tables and BIOS Parameter Blocks is done by the boot program in the boot sector itself or by other programs loaded through the boot process. A non-disk device such as
8128-630: The BIOS. Code in option ROMs runs before the BIOS boots the operating system from mass storage . These ROMs typically test and initialize hardware, add new BIOS services, or replace existing BIOS services with their own services. For example, a SCSI controller usually has a BIOS extension ROM that adds support for hard drives connected through that controller. An extension ROM could in principle contain operating system, or it could implement an entirely different boot process such as network booting . Operation of an IBM-compatible computer system can be completely changed by removing or inserting an adapter card (or
8255-508: The C64 allows for ten files to be opened at once). Thereafter, CHRIN and CHROUT prove useful for actually conducting input and output, respectively. CLOSE then closes a channel. Observe that no system call exists to "create" an I/O channel, for devices cannot be created or destroyed dynamically under normal circumstances. Likewise, no means exists for seeking, nor for performing "I/O control" functions such as ioctl () in Unix. Indeed,
8382-648: The FOR...NEXT construct are hard to create, often causing the programmer to rely on the GOTO command (this was later rectified in BASIC 3.5 with the addition of the DO, LOOP, WHILE, UNTIL , and EXIT commands). Flag variables often needed to be created to perform certain tasks. Later BASIC versions on Commodore and other platforms included a DELETE and RENUMBER command, as well as an AUTO line numbering command that would automatically select and insert line numbers according to
8509-667: The IBM BIOS and could not be taken advantage of without circumventing it. Since the AT-compatible BIOS ran in Intel real mode , operating systems that ran in protected mode on 286 and later processors required hardware device drivers compatible with protected mode operation to replace BIOS services. In modern PCs running modern operating systems (such as Windows and Linux ) the BIOS interrupt calls are used only during booting and initial loading of operating systems. Before
8636-502: The IEC (or IEEE port on the PET) port will slow the clock update by a few ticks. The RND function in Commodore BASIC can use the clock to generate random numbers; this is accomplished by RND(0) , however it is of relatively limited use as only numbers between 0 and 255 are returned. Otherwise, RND works the same as other implementations of Microsoft BASIC in that a pseudo-random sequence
8763-548: The KERNAL proves much closer to the Plan-9 philosophy here, where an application would open a special "command" channel to the indicated device to conduct such "meta" or "out-of-band" transactions. For example, to delete ("scratch") a file from a disk, the user typically will "open" the resource called S0:THE-FILE-TO-RMV on device 8 or 9, channel 15. Per established convention in the Commodore 8-bit world, channel 15 represents
8890-468: The X and Y registers: POKE 780 , 0 : POKE 781 , 0 : POKE 782 , 192 ; and the load routine would be called: SYS 65493 . A disk magazine for the C64, Loadstar , was a venue for hobbyist programmers, who shared collections of proto-commands for BASIC, called with the SYS address + offset command. From a modern programming point of view, the earlier versions of Commodore BASIC presented
9017-500: The analogue to the " CP/M BIOS ". The BIOS originally proprietary to the IBM PC has been reverse engineered by some companies (such as Phoenix Technologies ) looking to create compatible systems. With the introduction of PS/2 machines, IBM divided the System BIOS into real- and protected-mode portions. The real-mode portion was meant to provide backward compatibility with existing operating systems such as DOS, and therefore
9144-558: The array, not the size of each element, which is allocated dynamically. Unlike some other implementations of Microsoft BASIC, Commodore BASIC does not require string space to be reserved at the start of a program. Unlike other 8-bit machines such as the Apple II, Commodore's machines all have a built-in clock that is initialized to 0 at power on and updated with every tick of the PIA/VIA/TED/CIA timer, thus 60 times per second. It
9271-510: The boot sequence by inserting its own boot actions into it, by preventing the BIOS from detecting certain devices as bootable, or both. Before the BIOS Boot Specification was promulgated, this was the only way for expansion ROMs to implement boot capability for devices not supported for booting by the native BIOS of the motherboard. The user can select the boot priority implemented by the BIOS. For example, most computers have
9398-459: The card is not supported by the motherboard BIOS and the card needs to be initialized or made accessible through BIOS services before the operating system can be loaded (usually this means it is required in the boot process). An additional advantage of ROM on some early PC systems (notably including the IBM PCjr) was that ROM was faster than main system RAM. (On modern systems, the case is very much
9525-445: The command, GOTO , could be abbreviated G{Shift-O} (which resembled G Γ onscreen). Most such commands were two letters long, but in some cases they were longer. In cases like this, there was an ambiguity, so more unshifted letters of the command were needed, such as GO{Shift-S} ( GO♥ ) being required for GOSUB . Some commands had no abbreviated form, either due to brevity or ambiguity with other commands. For example,
9652-432: The command, INPUT had no abbreviation because its spelling collided with the separate INPUT# keyword, which was located nearer to the beginning of the keyword lookup table . The heavily used PRINT command had a single ? shortcut, as was common in most Microsoft BASIC dialects. Abbreviating commands with shifted letters is unique to Commodore BASIC. This tokenizing method had a glitch such that if one included
9779-492: The computer, and if it was lost the system settings could not be changed. The same applied in general to computers with an EISA bus, for which the configuration program was called an EISA Configuration Utility (ECU). A modern Wintel -compatible computer provides a setup routine essentially unchanged in nature from the ROM-resident BIOS setup utilities of the late 1990s; the user can configure hardware options using
9906-440: The device's configuration using default values. In addition, plug-in adapter cards such as SCSI , RAID , network interface cards , and video cards often include their own BIOS (e.g. Video BIOS ), complementing or replacing the system BIOS code for the given component. Even devices built into the motherboard can behave in this way; their option ROMs can be a part of the motherboard BIOS. An add-in card requires an option ROM if
10033-485: The expansion ROMs have finished executing and registering themselves with the BBS API. Also, if an expansion ROM wishes to change the way the system boots unilaterally, it can simply hook interrupt 19h or other interrupts normally called from interrupt 19h, such as interrupt 13h, the BIOS disk service, to intercept the BIOS boot process. Then it can replace the BIOS boot process with one of its own, or it can merely modify
10160-416: The extension ROM code takes over, typically testing and initializing the hardware it controls and registering interrupt vectors for use by post-boot applications. It may use BIOS services (including those provided by previously initialized option ROMs) to provide a user configuration interface, to display diagnostic information, or to do anything else that it requires. An option ROM should normally return to
10287-465: The first floppy disk drive or the first hard disk drive, even if there were two drives installed. On the original IBM PC and XT, if no bootable disk was found, the BIOS would try to start ROM BASIC with the interrupt call to interrupt 18h . Since few programs used BASIC in ROM, clone PC makers left it out; then a computer that failed to boot from a disk would display "No ROM BASIC" and halt (in response to interrupt 18h). Later computers would display
10414-435: The function is invoked on a C64 (38k BASIC memory), a negative amount of free BASIC memory will be displayed (adding 65535 to the reported number will obtain the correct amount of free memory). The PET and VIC-20 never had more than 32k of total memory available to BASIC, so this limitation did not become apparent until the C64 was developed. The FRE function on BASIC 3.5 and 7.0 corrected this problem and FRE on BASIC 7.0
10541-477: The idea of separating the BASIC routines from the operating system. It was further developed by several people, notably Robert Russell, who added many of the features for the VIC-20 and the C64. A simple, yet characteristic, example of using the KERNAL is given by the following 6502 assembly language subroutine (written in ca65 assembler format/syntax): This code stub employs the CHROUT routine, whose address
10668-482: The keyboard (device 0), cassette (device 1), the display interface (device 3), and printer (device 4 and 5), require no filenames to function, either assuming reasonable defaults or simply not needing them at all. BIOS In computing , BIOS ( / ˈ b aɪ ɒ s , - oʊ s / , BY -oss, -ohss ; Basic Input/Output System , also known as the System BIOS , ROM BIOS , BIOS ROM or PC BIOS )
10795-403: The keyboard and video display. The modern Wintel machine may store the BIOS configuration settings in flash ROM, perhaps the same flash ROM that holds the BIOS itself. Peripheral cards such as hard disk drive host bus adapters and video cards have their own firmware, and BIOS extension option ROM code may be a part of the expansion card firmware; that code provides additional capabilities in
10922-654: The keyboard, rudimentary text and graphics display functions and so forth). When using MS-DOS, BIOS services could be accessed by an application program (or by MS-DOS) by executing an interrupt 13h interrupt instruction to access disk functions, or by executing one of a number of other documented BIOS interrupt calls to access video display , keyboard , cassette, and other device functions. Operating systems and executive software that are designed to supersede this basic firmware functionality provide replacement software interfaces to application software. Applications can also provide these services to themselves. This began even in
11049-520: The line number and program statement are removed by the tokenizer. Program lines can be 80 characters total on most machines, but machines with 40 column text would cause the line to wrap around to the next line on the screen, and on the VIC-20, which had a 22 column display, program lines could occupy as many as four. BASIC 7.0 on the Commodore 128 increased the limit of a program line to 160 characters (four 40-column lines or two 80-column lines). By using abbreviations such as ? instead of PRINT , it
11176-441: The misspelling followed them along and stuck. According to early Commodore myth, and reported by writer/programmer Jim Butterfield among others, the "word" KERNAL is an acronym (or, more likely, a backronym ) standing for K eyboard E ntry R ead, N etwork, A nd L ink , which in fact makes good sense considering its role. Berkeley Softworks later used it when naming the core routines of its GUI OS for 8-bit home computers:
11303-527: The operating system's first graphical screen is displayed, input and output are typically handled through BIOS. A boot menu such as the textual menu of Windows, which allows users to choose an operating system to boot, to boot into the safe mode , or to use the last known good configuration, is displayed through BIOS and receives keyboard input through BIOS. Many modern PCs can still boot and run legacy operating systems such as MS-DOS or DR-DOS that rely heavily on BIOS for their console and disk I/O, providing that
11430-425: The option ROM scan is completed and all detected ROM modules with valid checksums have been called, the BIOS calls interrupt 19h to start boot processing. Post-boot, programs loaded can also call interrupt 19h to reboot the system, but they must be careful to disable interrupts and other asynchronous hardware processes that may interfere with the BIOS rebooting process, or else the system may hang or crash while it
11557-629: The optional parameter ,1 which will load a program into the memory address contained in the first two bytes of the file (these bytes are discarded and not retained in memory). If the ,1 parameter is not used, the program will load into the start of the BASIC program area, which widely differs between machines. Some Commodore BASIC variants supplied BLOAD and BSAVE commands that worked like their counterparts in Applesoft BASIC , loading or saving bitmaps from specified memory locations. The PET does not support relocatable programs and
11684-495: The point of successfully initializing a video display adapter. Options on the IBM PC and XT were set by switches and jumpers on the main board and on expansion cards . Starting around the mid-1990s, it became typical for the BIOS ROM to include a "BIOS configuration utility" (BCU ) or "BIOS setup utility", accessed at system power-up by a particular key sequence. This program allowed the user to set system configuration options, of
11811-416: The program. Line numbers can range from 0 to 65520 and take five bytes to store regardless of how many digits are in the line number, although execution is faster the fewer digits there are. Putting multiple statements on a line will use less memory and execute faster. GOTO and GOSUB statements will search downward from the current line to find a line number if a forward jump is performed, in case of
11938-420: The program. This is in contrast to business-oriented operating systems of the time like CP/M or MS-DOS , which typically booted into a command line interface . If a programming language was required on these platforms, it had to be loaded separately. While some versions of Commodore BASIC included disk-specific DLOAD and DSAVE commands, the version built into the Commodore 64 lacked these, requiring
12065-539: The programmer should avoid using them unless very large arrays are used that would exceed available memory if stored as floating point). Also, it is not possible to POKE or PEEK memory locations above 32767 with address defined as a signed integer. A period (.) can be used in place of the number 0 (thus 10 A = . instead of 10 A = 0 or 10 FOR A = . TO 100 instead of 10 FOR A = 0 to 100 ), this will execute slightly faster. The SYS statement, used to start machine language programs,
12192-464: The range of [32,256]. Conceivably, one can load a device driver binary into memory, patch the KERNAL I/O vectors, and from that moment forward, a new (virtual) device could be addressed. So far, this capability has never been publicly known as utilized, presumably for two reasons: (1) The KERNAL provides no means for dynamically allocating device IDs, and (2) the KERNAL provides no means for loading
12319-422: The recorder's counter display at the location of the file, but this was inaccurate and prone to error. With the PET (and BASIC 2.0), files from cassettes could be requested by name. The device would search for the filename by reading data sequentially, ignoring any non-matching filenames. The file system was also supported by a powerful record structure that could be loaded or saved to files. Commodore cassette data
12446-569: The reverse of this, and BIOS ROM code is usually copied ("shadowed") into RAM so it will run faster.) Option ROMs normally reside on adapter cards. However, the original PC, and perhaps also the PC XT, have a spare ROM socket on the motherboard (the "system board" in IBM's terms) into which an option ROM can be inserted, and the four ROMs that contain the BASIC interpreter can also be removed and replaced with custom ROMs which can be option ROMs. The IBM PCjr
12573-524: The screen). Since Commodore 8-bit machines other than the C128 cannot automatically boot disk software, the usual technique is to include a BASIC stub like 10 SYS 2048 to begin program execution. It is possible to automatically start software after loading and not require the user to type a RUN statement, this is done by having a piece of code that hooks the BASIC "ready" vector at $ 0302 . As with most other versions of Microsoft BASIC , if an array
12700-475: The screen. (The easter egg was well-obfuscated—the message did not show up in any disassembly of the interpreter.) The popular Commodore 64 came with BASIC v2.0 in ROM even though the computer was released after the PET/CBM series that had version 4.0 because the 64 was intended as a home computer, while the PET/CBM series were targeted at business and educational use where their built-in programming language
12827-451: The screen. If a line was prefixed with a line number, it was tokenized and stored in program memory. Lines not beginning with a number were executed by pressing the RETURN key whenever the cursor happened to be on the line. This marked a significant upgrade in program entry interfaces compared to other common home computer BASICs at the time, which typically used line editors , invoked by
12954-453: The sequence of the current seed value specified by the number. Since true random number generation is impossible with the RND statement, it is more typical on the C64 and C128 to utilize the SID chip's white noise channel for random numbers. BASIC 2.0 notoriously suffered from extremely slow garbage collection of strings. Garbage collection is automatically invoked any time a FRE function
13081-468: The source code of the flat-fee BASIC and further developed it internally for all their other 8-bit home computers. It was not until the Commodore 128 (with V7.0) that a Microsoft copyright notice was displayed. However, Microsoft had built an easter egg into the version 2 or "upgrade" Commodore Basic that proved its provenance: typing the command WAIT 6502, 1 would result in Microsoft! appearing on
13208-672: The stack set up by BIOS is unknown and its location is likewise variable; although the boot program can investigate the default stack by examining SS:SP, it is easier and shorter to just unconditionally set up a new stack. At boot time, all BIOS services are available, and the memory below address 0x00400 contains the interrupt vector table . BIOS POST has initialized the system timers, interrupt controller(s), DMA controller(s), and other motherboard/chipset hardware as necessary to bring all BIOS services to ready status. DRAM refresh for all system DRAM in conventional memory and extended memory, but not necessarily expanded memory, has been set up and
13335-422: The statement according to a lookup table. This meant that the statement up to where the high bit was set was accepted as a substitute for typing the entire command out. However, since all BASIC keywords were stored in memory as single byte tokens, this was a convenience for statement entry rather than an optimization. In the default uppercase-only character set, shifted characters appear as a graphics symbol; e.g.
13462-537: The system has a BIOS, or a CSM-capable UEFI firmware. Intel processors have reprogrammable microcode since the P6 microarchitecture. AMD processors have reprogrammable microcode since the K7 microarchitecture. The BIOS contain patches to the processor microcode that fix errors in the initial processor microcode; microcode is loaded into processor's SRAM so reprogramming is not persistent, thus loading of microcode updates
13589-479: The system is initialized, the first instruction of the BIOS appears at that address. If the system has just been powered up or the reset button was pressed (" cold boot "), the full power-on self-test (POST) is run. If Ctrl+Alt+Delete was pressed (" warm boot "), a special flag value stored in nonvolatile BIOS memory (" CMOS ") tested by the BIOS allows bypass of the lengthy POST and memory detection. The POST identifies, tests and initializes system devices such as
13716-405: The system timer-tick interrupt, which BIOS always uses at least to maintain the time-of-day count and which it initializes during POST, to be active and for the keyboard to work. The keyboard works even if the BIOS keyboard service is not called; keystrokes are received and placed in the 15-character type-ahead buffer maintained by BIOS.) The boot program must set up its own stack, because the size of
13843-660: The time, opening an I/O channel requires three system calls . The first typically sets the logical filename through the SETNAM system call. The second call, SETLFS , establishes the GPIB/ IEEE-488 "device" address to communicate with. Finally OPEN is called to perform the actual transaction. The application then used CHKIN and CHKOUT system calls to set the application's current input and output channels, respectively. Applications may have any number of concurrently open files (up to some system-dependent limit; e.g.,
13970-461: The type formerly set using DIP switches , through an interactive menu system controlled through the keyboard. In the interim period, IBM-compatible PCs—including the IBM AT —held configuration settings in battery-backed RAM and used a bootable configuration program on floppy disk, not in the ROM, to set the configuration options contained in this memory. The floppy disk was supplied with
14097-780: The user performs a restore using a pre-customised image provided by the OEM. Power users can copy the necessary certificate files from the OEM image, decode the SLP product key, then perform SLP activation manually. Some BIOS implementations allow overclocking , an action in which the CPU is adjusted to a higher clock rate than its manufacturer rating for guaranteed capability. Overclocking may, however, seriously compromise system reliability in insufficiently cooled computers and generally shorten component lifespan. Overclocking, when incorrectly performed, may also cause components to overheat so quickly that they mechanically destroy themselves. Some older operating systems , for example MS-DOS , rely on
14224-420: The user to specify the disk drive's device number (typically 8 or 9) to the standard LOAD command, which otherwise defaulted to tape. Another omission from the Commodore 64s BASIC 2.0 was a DIRECTORY command to display a disk's contents without clearing main memory. On the 64, viewing files on a disk was implemented as loading a "program" which when listed showed the directory as a pseudo BASIC program, with
14351-410: The whole 8-bit series. The KERNAL ROM occupies the last 8 KB of the 8-bit CPU's 64 KB address space ($ E000–$ FFFF). The jump table can be modified to point to user-written routines, for example, to integrate a fast loader so that its fast replacement routines are used system-wide or to replace the system text output routine with one that works in bitmapped mode rather than character mode. This use of
14478-709: The year 2000, most BIOSes provide ACPI , SMBIOS , VBE and e820 interfaces for modern operating systems. After operating systems load, the System Management Mode code is still running in SMRAM. Since 2010, BIOS technology is in a transitional process toward UEFI . Commodore BASIC Commodore BASIC , also known as PET BASIC or CBM-BASIC , is the dialect of the BASIC programming language used in Commodore International 's 8-bit home computer line, stretching from
14605-416: Was reverse engineered by some companies (such as Phoenix Technologies ) looking to create compatible systems. The interface of that original system serves as a de facto standard . The BIOS in older PCs initializes and tests the system hardware components ( power-on self-test or POST for short), and loads a boot loader from a mass storage device which then initializes a kernel . In the era of DOS ,
14732-480: Was added by Commodore and was not in the original Microsoft BASIC code, which featured only the USR function for invoking machine language routines. It automatically loads the CPU's registers with the values in $ 30C-$ 30F (C64, varies on other machines)--this can be used to pass data to machine language routines or as a means of calling kernal functions from BASIC (as an example, POKE 780 , 147 : SYS 65490 clears
14859-461: Was also "split" into two functions, one to display free BASIC program text memory and the other to display free variable memory. Many BASIC extensions were released for the Commodore 64, due to the relatively limited capabilities of its native BASIC 2.0. One of the most popular extensions was the DOS Wedge , which was included on the Commodore 1541 Test/Demo Disk. This 1 KB extension to BASIC added
14986-519: Was being entered, BASIC would constantly reorder program lines in memory so that the line numbers and pointers were all in ascending order. However, after a program was entered, manually altering the line numbers and pointers with the POKE commands could allow for out-of-order execution or even give each line the same line number. In the early days, when BASIC was used commercially, this was a software protection technique to discourage casual modification of
15113-429: Was frustrating to many users, some critics argued that it was ultimately beneficial since it forced the user to learn machine language. The limitations of BASIC 2.0 on the C64 led to use of built-in ROM machine language from BASIC. To load a file to a designated memory location, the filename, drive, and device number would be read by a call: SYS 57812 "filename" , 8 ; the location would be specified in
15240-474: Was halted using the RUN/STOP key, variable values would be preserved in RAM and could be PRINTed for debugging. The 128 even dedicated its second 64k bank to variable storage, allowing values to persist until a NEW or RUN command was issued. This, along with the advanced screen editor included with Commodore BASIC gave the programming environment a REPL -like feel; programmers could insert and edit program lines at any screen location, interactively building
15367-400: Was important, some programmers converted sections of BASIC programs to 6502 or 6510 assembly language that was loaded separately from a file or POKEd into memory from DATA statements at the end of the BASIC program, and executed from BASIC using the SYS command, either from direct mode or from the program itself . When the execution speed of machine language was too great, such as for
15494-433: Was named "CBIOS" (for "Compatibility BIOS"), whereas the "ABIOS" (for "Advanced BIOS") provided new interfaces specifically suited for multitasking operating systems such as OS/2 . The BIOS of the original IBM PC and XT had no interactive user interface. Error codes or messages were displayed on the screen, or coded series of sounds were generated to signal errors when the power-on self-test (POST) had not proceeded to
15621-399: Was part of the core Microsoft 6502 BASIC code, it was usually omitted in other implementations such as Applesoft BASIC . The native number format of Commodore BASIC, like that of its parent MS BASIC , was floating point . Most contemporary BASIC implementations used one byte for the characteristic ( exponent ) and three bytes for the mantissa . The accuracy of a floating point number using
15748-489: Was possible to fit more code on a single program line (which could take up two screen lines on 40-column displays - i.e., C64 or PET, or four lines on the VIC-20's 22-column display). This allowed for a slight saving on the overhead to store otherwise necessary extra program lines, but nothing more. All BASIC commands were tokenized and took up 1 byte (or two, in the case of several commands of BASIC 7 or BASIC 10) in memory no matter which way they were entered. Such long lines were
15875-490: Was presumed to be more heavily used. This saved manufacturing costs, as the V2 fit into smaller ROMs. A convenient feature of Commodore's ROM -resident BASIC interpreter and KERNAL was the full-screen editor . Although Commodore keyboards only have two cursor keys which reversed direction when the shift key was held, the screen editor allowed users to enter direct commands or to input and edit program lines from anywhere on
16002-458: Was recorded digitally, rather than less expensive (and less reliable) analog methods used by other manufacturers. Therefore, the specialized Datasette was required rather than a standard tape recorder. Adapters were available that used an analog-to-digital converter to allow use of a standard recorder, but these cost only a little less than the Datasette. The LOAD command may be used with
16129-406: Was stored in a ROM chip on the PC motherboard. In later computer systems, the BIOS contents are stored on flash memory so it can be rewritten without removing the chip from the motherboard. This allows easy, end-user updates to the BIOS firmware so new features can be added or bugs can be fixed, but it also creates a possibility for the computer to become infected with BIOS rootkits . Furthermore,
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