A
computer is more accurately referred to as a computer system consisting of
hardware, the physical components, and software, the programs
that control it.
A computer is a data processor. It can accept input (data and instructions),
remember the input by storing it in memory cells, process the stored input by
performing calculations and by making logical comparisons, and it can
communicate or output information.
Simply put, a computer is a machine that carries out instructions. The
set of instructions, which tell a computer to execute a series of
specific tasks, is called a program. A
computer is more accurately referred to as a computer system consisting of
hardware, the physical components, and software, the programs
that control it.
and the central processing unit (CPU) where processing and operations are
performed.
or mouse are the means
by which the computer takes in symbolic data and instructions.
or printer are the means by which the computer
sends out the symbolic results.
The CPU is the brain that controls the rest of the hardware. It is
made up of three different parts: the processor, arithmetic logic unit (ALU)
and internal memory. The processing unit or processor controls all the
other parts of the computer. It accepts input and stores it in the memory and
it interprets the instructions in a computer program. The arithmetic logic
unit (ALU) performs various operations, such as addition, subtraction,
multiplication, division, as well as others. The processor and the ALU use a
small amount of the internal memory; most data are stored in external
memory devices using hard disc or floppy disc that are attached to the
processor.
Computer design is based on devices with two states (open or closed circuits, on or off switches). The storage cells in the main memory are groups of electronic circuits, each of which is turned on (current flowing through it) or turned off (no current flowing through it). All the data and instructions stored in the computer are represented by strings of these "on" and "off" switches. Machine language is the language understood by the computer and is closely tied to the design of the computer. A bit, the smallest unit of storage in a computer, represents each "on" or "off" circuit. The smallest group of bits commonly addressed by present day CPU's is made up of eight bits, and is referred to as a byte. Because of this two state technology, machine language is written using two symbols, usually the digits 0 and 1. Therefore, machine language is also referred to as a binary language.
These strings of binary digits are very difficult for a human to decipher so a more compact form has been devised in which each group of three binary digits was replaced by a single number in the range 0-7 (octal digits). Machine language, which is a low-level language, may be different for various types of computers. Thus, the binary (base 2) sequence 010100011 010 000 010111 would be replaced by the octal (base 8) sequence 243 2 0 27.
A further development is the use of names to identify memory locations. These assembly languages use terms such as ADD (instead of the binary code 1101) and MOVE.L (A3),D0 (instead of the binary code 0010000000010011). An assembler translates the assembly language program into the machine language. But the language is still difficult and because it is specific to particular computers, the same assembly language program can not be run on different types of computers.
Computer software also includes software tools (editors, word processors, spreadsheet programs, and database management programs) and operating systems. An operating system is a set of programs that control the operation of the hardware of a computer and application programs submitted by users.
Exercise:
Define the following computer terms in your own words and relate them to the computer system you are using.
- hardware
- software
- input devices
- output devices
- central processing unit (CPU)
- arithmetic logic unit (ALU)
- machine language
- binary language
- compiler
- operating system.
