The commodore Plus/4 was released in 1984. The name refers to the four built in applications, a word processor, a spreadsheet, a database and a graphing program. The plus/4 was introduced as a productivity computer with the software built-in.

The machine was a complete flop in the US where it was called the "Minus/60" a pun on the difference with the successful commodore 64. The idea of the computer was to provide Commodore with a cheap alternative to machines of the competition, such as the Timex Sinclar range. Jack Tramiel wanted a slice of the budget computer market as he was convinced that Japanese companies where about to overtake the American home computer market, as this had happened with the audio and video markets.

The machine is internally much like the Commodore C16 and the C116, it is also built around the 8501 CPU and the TED video/sound chip. The Plus/4 had 64KByte of memory but the price point made it a direct competitor of Commodore's own C64. Existing peripheral devices, such as the 1531 datasette, or the 1551 disk drive were all incompatible, adding to the failure of the Plus/4.

The 7360 Text Editing Device or TED, was an integrated circuit made by MOS Technology Inc. It was a video chip that also contained sound generation hardware, DRAM refresh circuitry, interval timers, and keyboard input handling. It was specifically designed for the Commodore Plus/4 and the Commodore 16.

The video capabilities provided by TED were basically a subset of those in the VIC-II chip. The TED supports five video modes:

• 40x25 Text Mode, 8x8 pixel characters
• Multicolor text (4x8 pixels per character, double pixel width)
• Extended background color mode (8x8 pixels per character)
• 160x200 Multicolor Graphics
• 320x200 Hi-Res graphics

Commodore BASIC was a dialect of Microsoft BASIC, licensed by Commodore in 1977 for use in the PET 2001. It ran from ROM, freeing all RAM for user programs, and provided an immediate programming environment upon power-up. The interpreter was built on the 6502 processor, with tightly coded routines for tokenization, line storage, and execution. This structure allowed BASIC statements to be entered interactively, stored in memory as linked line records, and executed sequentially or via branching constructs. Commodore kept this design across its entire 8-bit product line, from the PET and VIC-20 to the Commodore 64 and beyond, creating a sense of continuity between machines.

Historically, Commodore BASIC differed from many other implementations in its limited feature set relative to machine capabilities. For example, the original PET BASIC lacked dedicated graphics or sound commands, requiring programmers to manipulate memory directly through PEEK and POKE. Even later versions, such as BASIC V2 on the C64, still omitted high-level graphics and sound statements, in contrast with Atari BASIC or BBC BASIC, which provided structured access to system hardware. Only with extended versions such as BASIC 3.5, 4.0, and 7.0 did Commodore add disk commands, string handling improvements, and more advanced features.

When compared to contemporaries, Commodore BASIC was often criticized as being underpowered, but its simplicity made it approachable. BBC BASIC, for example, incorporated structured programming constructs and inline assembler, whereas Commodore’s offering retained the line-numbered, unstructured style of early Microsoft BASIC. Atari BASIC, developed separately, emphasized graphics and sound integration through dedicated keywords. Commodore’s approach forced users to learn the underlying memory map, making them more technically literate about hardware but also raising the entry barrier for certain types of applications.

Despite its limitations, Commodore BASIC achieved massive popularity due to sheer reach. Millions of units shipped with it as the only built-in interface, ensuring every user interacted with it directly. Its ubiquity in schools, homes, and small businesses made it a de facto teaching language for a generation. Moreover, the reliance on PEEK and POKE, while cumbersome, fostered a culture of type-in listings and hardware exploration. This combination of accessibility, wide distribution, and necessity cemented Commodore BASIC’s role as one of the most influential programming environments of the late 1970s and 1980s.

• BASIC 1.0 (PET 2001, 1977)

  Computers: Commodore PET 2001
  Features: Essentially a stock Microsoft BASIC interpreter running in ROM, with support for integer and floating-point arithmetic, strings, arrays, and file operations for tape storage.
  Limitations: No disk commands, no advanced error trapping, and no machine-specific extensions. Designed as a minimal environment to ship the PET quickly.

• BASIC 2.0 (VIC-20, C64, C-MAX, 1981–1982)

  Computers: VIC-20, Commodore 64, Commodore MAX Machine
  Features: Nearly identical to BASIC 1.0 with minor bug fixes, provided the same core Microsoft BASIC functionality.
  Limitations: No disk drive commands, no dedicated graphics or sound statements. Hardware had to be accessed through POKE and PEEK.

• BASIC 3.5 (Commodore 16, C116, Plus/4, 1984)

  Computers: Commodore 16, Commodore 116, Commodore Plus/4
  Features: Added graphics and sound commands (GRAPHIC, CIRCLE, PAINT, SOUND, PLAY), integrated disk commands (DLOAD, DSAVE, DIRECTORY), plus utilities like RENUM and TRON/TROFF.
  Limitations: Still line-number oriented and lacked the structured programming richness of competitors like BBC BASIC.

• BASIC 4.0 (PET/CBM Business Series, 1979+)

  Computers: PET/CBM 4000 and 8000 series
  Features: Expanded disk support with DLOAD, DSAVE, DIRECTORY, COPY, and SCRATCH. Improved error handling suitable for commercial environments.
  Limitations: Focused on business and disk operations, no graphics or sound capabilities because target hardware lacked them.

• BASIC 7.0 (C-128, 1985)

  Computers: Commodore 128
  Features: Added high-level graphics (DRAW, CIRCLE, PAINT) and sound (PLAY, SOUND) commands, advanced disk operations, structured programming constructs like WHILE...WEND, RENUM, and support for memory banking and multi-mode operation.
  Limitations: Despite enhancements, still less sophisticated in structured constructs compared to BBC BASIC or contemporary Pascal-like systems.

• BASIC 10.0 (C-65 prototype, 1990–1991)

  Computers: Commodore 65 (prototype, unreleased commercially)
  Features: Extended support for high-resolution graphics and larger color palettes through VIC-III, up to 8 MB memory addressing, advanced string handling, and structured commands.
  Limitations: Never commercially released, so its practical impact was negligible despite advanced features.

The MOS 7501 and 8501 was introduced in 1984 and both chips are a variant of the 6510. Where the 6510 had 6 I/O ports, the 7501 and 8501 used all 8. However the CPU omits the pins for the non-maskable interrupt and the clock output. The 7501/8501 were used in the commodore 16, the commodore 116 and the Commodore Plus/4 computers. The I/O ports controlled the Datasette and the CBM Bus interface.

The 7501 and 8501 were functionally equivalent, but the manufacturing process was different. The 7501 was manufactured with HMOS-1, and the 8501 was manufactured with HMOS-2. HMOS-2 used a channel length of 2 microns against the 3 microns of HMOS-1.