CAT | Introduction to Computer
All the parts we have reviewed so far are usually required for the computer to function. Some other parts, not required, can also be connected to the computer to complement it. A peripheral is an object attached to the computer to help it perform some necessary assignments none of the other parts can handle. In most scenarios, no peripheral is required but nowadays, it is unusual for a computer not to have any peripheral at all. The most used peripherals are the printer, a digital camera, a scanner, a projector, an external drive (such as an external CD burner for an old computer or an external hard drive), etc.
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A parity bit is a bit that is added to ensure that the number of bits with the value one in a set of bits is even or odd. Parity bits are used as the simplest form of error detecting code.
There are two variants of parity bits: even parity bit and odd parity bit. When using even parity, the parity bit is set to 1 if the number of ones in a given set of bits (not including the parity bit) is odd, making the number of ones in the entire set of bits (including the parity bit) even. When using odd parity, the parity bit is set to 1 if the number of ones in a given set of bits (not including the parity bit) is even, keeping the number of ones in the entire set of bits (including the parity bit) odd. In other words, an even parity bit will be set to “1″ if the number of 1′s + 1 is even, and an odd parity bit will be set to “1″ if the number of 1′s +1 is odd.
| 7 bits of data
(number of 1s) |
8 bits including parity | |
| even | odd | |
| 0000000 (0) | 00000000 | 10000000 |
| 1010001 (3) | 11010001 | 01010001 |
| 1101001 (4) | 01101001 | 11101001 |
| 1111111 (7) | 11111111 | 01111111 |
Basic Input/Output System (BIOS) software is built into the PC, and is the first code run by a PC when powered on (‘boot firmware’). The primary function of the BIOS is to set up the hardware and load and start an operating system. When the PC starts up, the first job for the BIOS is to initialize and identify system devices such as the video display card, keyboard and mouse, hard disk drive, optical disc drive and other hardware. The BIOS then locates software held on a peripheral device (designated as a ‘boot device’), such as a hard disk or a CD/DVD, and loads and executes that software, giving it control of the Personal Computer. This process is known as booting, or booting up, which is short for bootstrapping.
BIOS software is stored on a non-volatile ROM chip built into the system on the motherboard. The BIOS software is specifically designed to work with the particular type of system in question, including having knowledge of the workings of various devices that make up the complementary chipset of the system. In modern computer systems, the BIOS chip’s contents can be rewritten, allowing BIOS software to be upgraded.
BIOS will also have a user interface (or UI for short). Typically this is a menu system accessed by pressing a certain key on the keyboard when the PC starts. In the BIOS UI, a user can:
- configure hardware
- set the system clock
- enable or disable system components
- select which devices are eligible to be a potential boot device
- set various password prompts, such as a password for securing access to the BIOS UI functions itself and preventing malicious users from booting the system from unauthorized peripheral devices.
The BIOS provides a small library of basic input/output functions used to operate and control the peripherals such as the keyboard, text display functions and so forth, and these software library functions are callable by external software. In the IBM PC and AT, certain peripheral cards such as hard-drive controllers and video display adapters carried their own BIOS extension Option ROM, which provided additional functionality. Operating systems and executive software, designed to supersede this basic firmware functionality, will provide replacement software interfaces to applications.
Firmware is a combination of software and hardware. Computer chips that have data or programs recorded on them are firmware. These chips commonly include the following:
- ROMs (read-only memory)
- PROMs (programmable read-only memory)
- EPROMs (erasable programmable read-only memory)
Firmware in PROM or EPROM is designed to be updated if necessary through a software update.
An interface on a computer to which you can connect a device. Personal computers have various types of ports. Internally, there are several ports for connecting disk drives, display screens, and keyboards. Externally, personal computers have ports for connecting modems, printers, mice, and other peripheral devices.
Electronically, hardware ports can almost always be divided into two groups based on the signal transfer:
- Serial ports send and receive one bit at a time via a single wire pair.
- Parallel ports send multiple bits at the same time over several sets of wires.
Almost all personal computers come with a serial RS-232C port or RS-422 port for connecting a modem or mouse and a parallel port for connecting a printer.
What is CMOS?
Complementary metal–oxide–semiconductor (CMOS) is a technology for constructing integrated circuits. CMOS technology is used in microprocessors, static RAM, and other digital logic circuits.
