Central Processing Unit: Parts, Definition & Function - Computer Awareness Notes

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Central Processing Unit: Parts, Definition & Function
Central Processing Unit (CPU)
The Central Processing Unit (CPU) is the brain of the computer. It performs all the calculations and computations necessary for performing basic arithmetic, logical, control and input/output (I/O) operations.
Computer Organization
Computer Organization provides a logical explanation using block diagrams and arrows to describe how a computer works i.e. how the various parts of the CPU interact and how it works with the input and output devices to make the computer work.
The block diagram above represents a uni-processor CPU computer. Black lines indicate data flow, whereas red lines indicate control flow; arrows indicate flow directions.
Computer Processor/Microprocessor
Computer Processor
Traditionally, the term “CPU” refers to a processor, more specifically to its processing unit and control unit (CU), distinguishing these core elements of a computer from external components such as main memory and I/O circuitry. A central processing unit (CPU) is the electronic circuitry within a computer that carries out the instructions of a computer program by performing the basic arithmetic, logical, control and input/output (I/O) operations specified by the instructions.
Most modern processors are microprocessors, meaning, several components (Arithmetic Logic Unit, Control Unit, etc.,) contained on a single integrated circuit (IC) chip. An IC that contains a CPU may also contain memory, peripheral interfaces, and other components of a computer; such integrated devices are variously called micro controllers or systems on a chip (SoC). Some computers employ a multi-core processor, which is a single chip containing two or more CPUs called “cores”.
Parts of a Processor/Central Processing Unit(CPU)
Control Unit
The control unit (CU) is a component of a computer’s central processing unit (CPU) that directs operation of the processor. It tells the computer’s memory, arithmetic/logic unit and input and output devices how to respond to a program’s instructions.
Arithmetic Logic Unit
An arithmetic logic unit (ALU) is a digital circuit used to perform arithmetic and logic operations. It represents the fundamental building block of the central processing unit (CPU) of a computer.
Memory Unit
This unit can store instructions, data and intermediate results. This unit supplies information to the other units of the computer when needed.
In a computer, a register is one of a small set of data holding places that are part of a computer processor. A register may hold a computer instruction, a storage address, or any kind of data. Some instructions specify registers as part of the instruction.

Processor Cores
Single Core
A chip with one CPU (one processing unit).
Multi-Core Processor
A multi-core processor is a single computing component with two or more independent actual processing units (called “cores”), which are the units that read and execute program instructions.
Instruction Pipe-Lining
A pipeline is a set of data processing elements connected in series, where the output of one element is the input of the next one. The elements of a pipeline are often executed in parallel or in time-sliced fashion. By using the concept of pipe lining the CPU processes instructions at a faster rate.
FLOPS (Floating-Point Operations Per Second)
FLOPS or flops (an acronym for floating-point operations per second) is a measure of computer performance, useful in fields of scientific calculations that make heavy use of floating-point calculations. For such cases it is a more accurate measure than the generic instructions per second.
Processor/Memory Speed Measurement in Clock Cycles
1. Hz: Hertz (equal to one cycle per second)
2. KHz: Kilo Hertz (1000 cycles per second)
3. MHz: Mega Hertz (1 Million cycles per second)
4. GHz: Giga Hertz (1000 Million/1 Billion cycles per second)
Processor Speed Measurement in terms of Operations Per Second
1. FLOPS: Floating Point Operations Per Second
2. MFLOPS: Million Floating point Operations Per Second
3. MIPS: Millions of Instruction Per Second
4. TFLOPS: Tera Floating-Point Operations Per Second
Acronyms of the Logical Units of a Computer
1. CPU: Central Processing Unit
2. ALU: Arithmetic Logic Unit
3. MCB: Memory Control Block
4. CU: Control Unit
5. DMA: Direct Memory Access
Abbreviations in Integrated Circuits
1. IC: Integrated Circuit
2. SSI: Small Scale Integrated Circuit
3. MSI: Medium Scale Integrated Circuit
4. LSI: Large Scale Integrated Circuit
5. VLSI: Very Large Scale Integrated Circuit