INPUT UNIT • The input unit consists of the devices which accept the data and instructions from the user and communicates it to the CPU. • The various input devices are: keyboard, mouse, joystick, trackball etc. OUTPUT UNIT • It provides the result of the various operations performed by the CPU to the user. • The various output devices are: printers, monitors, loudspeakers etc. CENTRAL PROCESSING UNIT (CPU) • The CPU is the heart and nerve centre of the computer. • It fetches the instruction and data from the peripheral devices and performs all the arithmetic operations, takes logical decision and control the operation of all other units. Various sub-blocks of the central processing unit are: • Arithmetic and Logic Unit (ALU) • Timing & Control Unit • Registers ARITHMETIC AND LOGIC UNIT (ALU)
• This unit performs all the logical and arithmetic operations. • Various arithmetic operations are: addition, subtraction, increment and decrement etc. • Various logical operations are: AND, OR, NOT, XOR, etc. TIMING AND CONTROL UNIT • This unit controls the entire operations being performed by the system. • It controls the operations of ALU, input/output devices and memory unit. • This unit interprets the instructions and generates various timing and control signals. REGISTERS • A register is a very small amount of very fast memory that is built into the CPU in order to store the current data and instructions which are being executed by the CPU. MEMORY UNIT • • • • It stores the program statement and the data i.e. the information supplied from the input unit. It also stores the final output. This is connected to the CPU by means of a bidirectional bus. The CPU processes the information as taken from the memory and performs the operations in the ALU section. • The results are either transferred to the output unit or stored in the memory for later use by the CPU.
A MICRO-COMPUTER • As the name implies, microcomputers are small computers. • The block diagram of the microcomputer is similar to the computer except that the central processing unit of the microcomputer is contained in a single IC called the microprocessor. • A microprocessor is a LSI (Large Scale Integration) IC that does almost all the functions of the CPU. • It is also defined as a CPU contained in a single chip. The basic function of the microprocessor is: • to fetch the instructions stored in the main memory • identify the operations and the devices involved in it • and accordingly generate control signals to determine when a given action is to take place. We can say that a CPU is known as computer with a microprocessor as its Microcomputer. Some Definitions MICROPROCESSOR: • The central processing unit built on a single IC is called Microprocessor. • A microprocessor (sometimes abbreviated as µP) is a digital electronic component with miniaturized transistors on a single semiconductor integrated circuit (IC). • One or more microprocessors typically serve as a central processing unit (CPU) in a computer system or handheld device
MICROCOMPUTER: • A digital computer, in which one microprocessor has been provided to act as a CPU, is called Microcomputer. • A desktop computer, laptop, notebook, palmtop, etc. contain one microprocessor to act as a CPU and hence they come under the category of microcomputer. • The term microcomputer is generally synonymous with personal computer. MULTIPROCESSOR SYSTEM: • The CPU of a large powerful digital computer contains more than one microprocessor. • High-end powerful servers, mainframe computers, supercomputers, etc. contain more than one microprocessor to act as CPU. • A computer whose CPU contains more than one microprocessor is called Multiprocessor System.