Editing Commodore 64 (section)

== Software ==
{{Main|Commodore 64 software}}
In 1982, the C64's graphics and sound capabilities were rivaled only by the [[Atari 8-bit computers]] and appeared exceptional when compared with the popular [[Apple II]]. The C64 is often credited with starting the [[demoscene]] subculture (see [[Commodore 64 demos]]). It is still being actively used in the demoscene,<ref>{{cite web|url=http://www.lyonlabs.org/commodore/c4-2008/c4-2008.html |title=C=4 Expo 2008 |publisher=Lyonlabs.org |access-date=April 22, 2013}}</ref> especially for music (its SID sound chip even being used in special sound cards for PCs, and the [[Elektron SidStation]] synthesizer). Even though other computers quickly caught up with it, the C64 remained a strong competitor to the later [[video game console]]s [[Nintendo Entertainment System]] (NES) and [[Master System]], thanks in part to its by-then established software base, especially outside North America, where it comprehensively outsold the NES.{{citation needed|date=January 2012}}

Because of lower incomes and the domination of the [[ZX Spectrum]] in the UK, almost all British C64 software used cassette tapes. Few cassette C64 programs were released in the US after 1983 and, in North America, the diskette was the principal method of software distribution. The cartridge slot on the C64 was also mainly a feature used in the computer's first two years on the US market and became rapidly obsolete once the price and reliability of 1541 drives improved. A handful of PAL region games used bank switched cartridges to get around the 16&nbsp;KB memory limit.

=== BASIC ===
{{Main|Commodore BASIC}}
[[File:Simons Basic Splash Screen.gif|thumb|right|The [[Simons' BASIC]] interpreter start-up screen. Note the altered background and text colors (vs the ordinary C64 blue tones) and the {{nowrap|8 [[kilobyte|KB]]}} reduction of available BASIC-interpreter program memory allocation, due to the [[address space]] used by the cartridge.]]

As is common for home computers of the early 1980s, the C64 comes with a BASIC interpreter, in ROM. KERNAL, I/O, and tape/disk drive operations are accessed via custom BASIC language commands. The disk drive has its own interfacing [[microprocessor]] and ROM (firmware) I/O routines, much like the earlier CBM/PET systems and the Atari 400 and Atari 800. This means that no memory space is dedicated to running a [[disk operating system]], as was the case with earlier systems such as the Apple&nbsp;II and [[TRS-80]].

Commodore BASIC 2.0 is used instead of the more advanced BASIC&nbsp;4.0 from the PET series, since C64 users were not expected to need the disk-oriented enhancements of BASIC&nbsp;4.0. The company did not expect many to buy a disk drive, and using BASIC&nbsp;2.0 simplified VIC-20 owners' transition to the 64.<ref name="heimarck198706">{{cite news|url=https://archive.org/stream/1987-06-computegazette/Compute_Gazette_Issue_48_1987_Jun#page/n21/mode/2up|title=When 2 + 3.5 + 4 = 7 / The Evolution of Commodore BASIC|date=June 1987|work=Compute!'s Gazette|pages=20–26|access-date=June 30, 2014|author=Heimarck, Todd}}</ref> "The choice of BASIC&nbsp;2.0 instead of 4.0 was made with some soul-searching, not just at random. The typical user of a C64 is not expected to need the direct disk commands as much as other extensions, and the amount of memory to be committed to BASIC were to be limited. We chose to leave expansion space for color and sound extensions instead of the disk features. As a result, you will have to handle the disk in the more cumbersome manner of the 'old days'."<ref>{{cite magazine |url=https://archive.org/details/Commodore_The_Microcomputer_Magazine_Volume_03_Number_04_1982-08_Commodore_US/page/n64/mode/1up | title=BASIC Programming on the Commodore 64 | volume=3 |number=4 | magazine=Commodore Magazine |date=August 1982 |page=65 |via=Internet Archive}}</ref>

The version of [[Microsoft BASIC]] is not very comprehensive and does not include specific commands for sound or graphics manipulation, instead requiring users to use the "[[PEEK and POKE]]" commands to access the graphics and sound chip registers directly. To provide extended commands, including graphics and sound, Commodore produced two different cartridge-based extensions to BASIC&nbsp;2.0: [[Simons' BASIC]] and [[Super Expander 64]]. Other languages available for the C64 include [[Pascal (programming language)|Pascal]], [[C (programming language)|C]],<ref>{{cite web|author=ShadowM |url=https://www.lyonlabs.org/commodore/onrequest/powerc/index.html |title=Power C for the Commodore 64 |website=Lyonlabs.org |date=May 2, 2019 |access-date=February 9, 2020}}</ref><ref>{{cite web|url=http://www.clipshop.ca/Aztec/compilers.htm#commodore |title=Wonderfully Ancient Aztec C Compilers |website=Clipshop.ca |date=July 15, 1986 |access-date=March 18, 2017}}</ref> [[Logo (programming language)|Logo]], [[Forth (programming language)|Forth]],<ref>{{cite web |author=Handic Software |title=C64-FORTH  |date=1983 |work=Commodore Info |oclc=19379992 |url=https://www.commodore-info.com/cartridge/item/handic_c64-forth/en/desktop}}</ref> and [[FORTRAN]]. Compilers for BASIC&nbsp;2.0 such as Petspeed&nbsp;2 (from Commodore), Blitz (from Jason Ranheim), and Turbo Lightning (from [[Ocean Software]]) were produced. Most commercial C64 software was written in assembly language, either cross-developed on a larger computer, or directly on the C64 using a machine code monitor or an assembler. This maximized speed and minimized memory use. Some games, particularly adventures, used high-level scripting languages and sometimes mixed BASIC and machine language.

=== Alternative operating systems ===
Many third-party operating systems have been developed for the C64. As well as the original [[GEOS (8-bit operating system)|GEOS]], two third-party GEOS-compatible systems have been written: Wheels and GEOS megapatch. Both of these require hardware upgrades to the original C64. Several other operating systems are or have been available, including WiNGS OS, the Unix-like LUnix, operated from a command-line, and the embedded systems OS [[Contiki]], with full GUI.  Other less well-known OSes include ACE, Asterix, DOS/65, and [[GeckOS]]. C64 OS is commercially available today and under active development. It features a full GUI in character mode, and many other modern features. A version of [[CP/M]] was released, but this requires the addition of an external [[Zilog Z80|Z80]] processor to the expansion bus. Furthermore, the Z80 processor is underclocked to be compatible with the C64's memory bus, so performance is poor compared to other CP/M implementations. C64 CP/M and C128 CP/M both suffer a lack of software; although most commercial CP/M software can run on these systems, software media is incompatible between platforms. The low usage of CP/M on Commodores means that software houses saw no need to invest in mastering versions for the Commodore disk format. The C64 CP/M cartridge is also not compatible with anything except the early 326298 motherboards.{{citation needed|date=April 2018}}

=== Networking software ===
During the 1980s, the Commodore 64 was used to run [[bulletin board system]]s using software packages such as [[Steve Punter|Punter]] BBS, Bizarre 64, [[Blue Board (software)|Blue Board]], C-Net, [[Color 64]], CMBBS, C-Base, DMBBS, Image BBS, EBBS, and The Deadlock Deluxe BBS Construction Kit, often with [[sysop]]-made modifications. These boards sometimes were used to distribute [[cracked software]]. As late as December 2013, there were 25 such Bulletin Board Systems in operation, reachable via the [[Telnet]] protocol.<ref>{{cite web|url=http://cbbsoutpost.servebbs.com |title=Commodore BBS Outpost |website=Cbbsoutpost.servebbs.com |access-date=March 18, 2017}}</ref> There were major commercial [[online services]], such as [[Compunet]] (UK), [[CompuServe]] (US{{snd}} later bought by [[America Online]]), [[The Source (online service)|The Source]] (US), and [[Minitel]] (France) among many others. These services usually required custom software which was often bundled with a [[modem]] and included free online time as they were billed by the minute. [[Quantum Link]] (or Q-Link) was a US and Canadian online service for Commodore 64 and 128 personal computers that operated from November 5, 1985, to November 1, 1994. It was operated by [[Quantum Computer Services]] of [[Vienna, Virginia|Vienna]], Virginia, which in October 1991 changed its name to [[America Online]] and continued to operate its [[AOL]] service for the [[IBM PC compatible]] and Apple [[Macintosh]]. Q-Link was a modified version of the [[PlayNET]] system, which [[Control Video Corporation]] (CVC, later renamed Quantum Computer Services) licensed.

=== Online gaming ===
{{Further|History of massively multiplayer online games}}
The first graphical character-based interactive environment is ''[[Club Caribe]]''. First released as ''[[Habitat (video game)|Habitat]]'' in 1988, ''Club Caribe'' was introduced by [[LucasArts]] for [[Q-Link]] customers on their Commodore 64 computers. Users could interact with one another, chat and exchange items. Although the game's [[open world]] was very basic, its use of online avatars and the combination of chat and graphics was revolutionary. Online graphics in the late 1980s were severely restricted by the need to support modem data transfer rates as low as 300 [[bits per second]]. Habitat's graphics were stored locally on floppy disk, eliminating the need for network transfer.<ref>{{cite news|url=http://sdtimes.com/sd-times-blog-strangest-software-project-ive-ever-run/|title=The Strangest Software Project I've Ever Run|first=Alex|last=Handy|work=[[SD Times]]|date=September 23, 2014|access-date=August 19, 2015}}</ref>