IBM PC
Introduction
The IBM Personal Computer, commonly known as the IBM PC, is a microcomputer introduced by International Business Machines Corporation in 1981. The IBM PC model number 5150 was designed with a focus on business and professional use, and it played a pivotal role in the development and standardization of the personal computer industry. The IBM PC's architecture became the de facto standard for personal computers, leading to widespread adoption and the emergence of a vast ecosystem of compatible hardware and software.
Development and Design
The development of the IBM PC was initiated in response to the growing popularity of microcomputers in the late 1970s. IBM's Entry Systems Division, led by Don Estridge, was tasked with creating a competitive personal computer. The team opted for an open architecture, which allowed third-party manufacturers to produce compatible components and peripherals. This decision was instrumental in the rapid proliferation of the IBM PC and its clones.
The IBM PC was built around the Intel 8088 microprocessor, an 8-bit processor with a 16-bit address bus, running at a clock speed of 4.77 MHz. The choice of the Intel 8088 was influenced by its compatibility with existing software and its cost-effectiveness. The system included 16 KB of RAM, expandable to 640 KB, and a 5.25-inch floppy disk drive for storage. The IBM PC also featured a modular design, with five expansion slots for additional hardware.
Operating System and Software
The IBM PC initially shipped with PC DOS, an operating system developed by Microsoft and based on 86-DOS, which was acquired from Seattle Computer Products. PC DOS provided a command-line interface and supported a range of software applications, including word processors, spreadsheets, and database management systems. The choice of PC DOS as the operating system contributed to the IBM PC's success, as it allowed for compatibility with a wide array of software.
In addition to PC DOS, the IBM PC supported other operating systems such as CP/M-86 and UCSD p-System. However, PC DOS quickly became the dominant operating system due to its ease of use and the growing library of compatible software.
Hardware and Peripherals
The IBM PC's hardware architecture was designed to be flexible and expandable. The system unit housed the motherboard, which included the CPU, RAM, and ROM. The motherboard also featured five expansion slots, allowing users to add additional hardware such as graphics cards, memory expansion cards, and network adapters.
The IBM PC was available with a variety of peripherals, including:
- Monochrome display adapter (MDA): Provided text-only display capabilities with a resolution of 80x25 characters.
- Color graphics adapter (CGA): Offered both text and graphics display capabilities with a maximum resolution of 320x200 pixels.
- Floppy disk drives: Supported both single-sided and double-sided 5.25-inch floppy disks with capacities of 160 KB and 320 KB, respectively.
- Hard disk drives: Later models supported hard disk drives with capacities ranging from 10 MB to 20 MB.
- Printers: IBM offered a range of dot matrix and daisy wheel printers for the IBM PC.
Impact and Legacy
The IBM PC's introduction had a profound impact on the personal computer industry. Its open architecture and use of off-the-shelf components allowed other manufacturers to create compatible systems, leading to the rise of the IBM PC compatible market. Companies such as Compaq, Dell, and Hewlett-Packard produced IBM PC clones, which further popularized the platform and drove down prices.
The IBM PC also influenced software development, as developers created applications specifically for the PC DOS environment. This led to the growth of a robust software ecosystem, including popular programs like Lotus 1-2-3, WordPerfect, and AutoCAD.
The legacy of the IBM PC is evident in the continued use of the x86 architecture in modern personal computers. The principles of open architecture and compatibility established by the IBM PC remain foundational to the industry.
Technical Specifications
The IBM PC 5150's technical specifications include:
- **CPU**: Intel 8088, 4.77 MHz
- **RAM**: 16 KB, expandable to 640 KB
- **ROM**: 40 KB
- **Storage**: 5.25-inch floppy disk drive, optional hard disk drive
- **Display**: Monochrome or color graphics adapter
- **Expansion Slots**: 5 ISA slots
- **Ports**: Parallel port, serial port, keyboard port
- **Operating System**: PC DOS, CP/M-86, UCSD p-System
Variants and Successors
Following the success of the IBM PC 5150, IBM released several variants and successors, including:
- **IBM PC XT**: Introduced in 1983, the XT featured an integrated hard disk drive and eight expansion slots.
- **IBM PC AT**: Released in 1984, the AT utilized the more powerful Intel 80286 processor and supported enhanced graphics and memory capabilities.
- **IBM Portable PC**: A portable version of the IBM PC, introduced in 1984, designed for business professionals on the go.
- **IBM PS/2**: Launched in 1987, the PS/2 series introduced the Micro Channel Architecture (MCA) and aimed to modernize the IBM PC line.