It is the physical tangible and permanent components of a computer.
Computers, in spite of their seeming complexity, are not truly that difficult to understand in simplest terms computers process data. They take raw data (input), manipulate or process them in some specific way (process), and give back new data in the form of documents and reports (output). These are the most fundamental activities of computing.
A computer must be surrounded by devices to feed data, process information and provide results. A computer system consists of five basic units:
1) Input device (s)
2) A control unit (program controller)
3) An arithmetic and logic unit (ALU)
4) Storage devices (main and auxiliary memories), and
5) Output devices(s)
The control unit together with the arithmetic /logic unit and main storage unit constitutes the central processing unit (CPU) of the system. The control unit assumes the role of the coordinator and links all the other units in the system. Its main functions are (a) to control the transfer of information between various storage devices and the input and output devices and (b) to initiate the appropriate functions by the arithmetic unit.
The arithmetic and logic unit performs the actual arithmetic and logical processing. For example, if two numbers A and B are to be added, the control unit selects number A from its address in the memory and loads it into the arithmetic unit. Then the value of B is selected and added to A in the arithmetic unit.
The storage devices of a computer are used to hold many types of information. External or auxiliary devices such as the magnetic drum, magnetic disk, magnetic card and magnetic tape are used to store additional information that is required by the computer.
A computer can have one or more of the following input devices:
1) Key boards
2) Joy Sticks
4) Light pens
5) Digitizer tablets
6) Disk drives.
On the other hand, the output devices include
1) Video display screens
3) Voice synthesizers
5) Disk drives.
The processing in Computers:
The computer processes information in several ways, it can:
1) Enter data
2) Calculate (like add, subtract, multiply, and divide numbers)
3) Store data for later use
4) Retrieve the data stored previously
5) Compare data
6) Sort the lists of data in numerical or alphabetical order.
7) Display or print in any format.
Individually, all these processes may seem to be quite simple. But all these processes may be combined in various ways to do complex tasks.
Bit and Bytes:
Bit: It is one binary digit either 1 or 0.
Bytes: A sequence of adjacent binary digits operated upon as a unit in a computer and usually shorter than a word.
The processor of a computer consist of many thousands of logic circuits, storage registers, and associated circuits that enable the computer to manipulate and transform data. The logic circuits are programmed to allow current to flow or not to flow. Like an ordinary light switch, they can be either ‘no’ or ‘off’. In simple words this can be represented as 1 (one) or 0 (zero) where 1 means ‘on’ and 0 mean ‘off’. The binary number system which was has only two digits zero (0) and one (1) is conveniently used to express the two possible states. Taken by themselves these ones and zeros mean nothing, but taken in pattern or combinations (of say 8 or 16) they can represent a number or a letter of the alphabet.
Each numeral in the binary number is a binary digit, usually shortened to bit. A bit is one binary either 1 or 0.
The CPU uses the computer’s memory to hold pieces of information while it works with them. In other words, it uses the computer’s memory as a scratch pad for calculations. There are two basic types of memory, temporary data memory and permanent data memory. Temporary data memory is also referred to as internal memory or working memory. More popularity it is known as RAM (Random Access Memory) permanent data memory may include floppy disk, hard disk etc.
Random Access Memory (RAM):
RAM is the built in memory of the computer. RAM holds information only while the computer is on. When you turn off or reset the computer, the information disappears unless it is saved on a storage device.
The most common unit of measure of computer is the byte, as we have seen earlier. Today’s personal computers commonly have the memory of 4 to 32 million bytes. Kilobyte and megabyte are the two most common terms used to measure the memory. A kilobyte is, 1,024 bytes of memory, and a megabyte is 1,024 kilobytes – or 1,048, 576 bytes. Kilobytes and megabyte are often abbreviated as KB and MB. So a computer with 4 MB of memory actually has 4 X 1,048, 576 = 4,194,304 bytes.
Read only Memory (ROM):
Read only memory (ROM) is special memory circuit chip that has been loaded with the program or data at the factory. They provide special data and programs required for the operation of the computer. Data cannot be “written” on to a ROM, but only “read” from it. The ROM cartridge is plugged into a special connector slot on a computer and provides access to stored programs in the same way as the floppy disks, except that programs and data cannot be saved to the ROM since it is a read-only device.