• 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.
MICROPROCESSOR CHARACTERISTICS Instruction Set: The set of instructions that a microprocessor can understand. Bandwidth: The number of bits processed in a single instruction. Capability: It depends upon the number of instructions and capability of each instruction. Clock Speed: • The clock speed determines how many operations per second the processor can perform. It is also called Clock Rate. • Every computer contains an internal clock that regulates the rate at which instructions are executed and synchronizes the various computer components. • The faster the clock, the more instructions the CPU can execute per second. • Clock speeds are expressed in megahertz (MHz) or gigahertz (GHz). • The microprocessors of personal computers have clock speeds of anywhere from 300 MHz to over 3.8 GHz. Word Length: • It depends upon the width of internal data bus, registers, ALU etc. • An 8-bit microprocessor can process 8 bit data at a time. • A processor with longer word length is more powerful and can process data at a faster speed as compared to processor with shorter word length. • The word length ranges from 4 bits for small microprocessor, to 64 bits for high-end microcomputers.