CPF Reviewer
CPF Reviewer
CPF Reviewer
Limitations of Computers
• Computer can only perform tasks that it has been programmed to do.
• Computer cannot do any work without instructions from the user.
• It executes instructions as specified by the user and does not take its own decisions.
CLASSIFICATION OF COMPUTER
(1) Microcomputers,
(2) Minicomputers,
(3) Mainframe computers, and
(4) Supercomputer.
Microcomputers
- small, low-cost and single-user digital computer.
- Consist of CPU, input unit, output unit, storage unit and the software.
1.Desktop Computer or Personal Computer (PC)
the most common type of microcomputer. It is a stand-alone machine that can be placed on the desk.
It is not very expensive and is suited to the needs of a single user at home, small business units, and
organizations.
2.Notebook Computers or Laptop
resemble a notebook.
They are portable and have all the features of a desktop computer.
3. Netbook These
smaller notebooks optimized for low weight and low cost, and are designed for accessing web-based
applications.
4. Tablet Computer
has features of the notebook computer but it can accept input from a stylus or a pen instead of the keyboard
or mouse.
Tablet computer are the new kind of PCs.
5. Handheld Computer or Personal Digital Assistant (PDA)
a small computer that can be held on the top of the palm.
PDA uses a pen or a stylus for input.
do not have a disk drive.
They have a limited memory and are less powerful.
6. Smart Phones
cellular phones that function both as a phone and as a small PC.
They may use a stylus or a pen, or may have a small keyboard. They can be connected to the Internet
wirelessly.
Minicomputers.
are digital computers, generally used in multi-user systems.
The users can access the minicomputer through their PCs or terminal.
Mainframe Computers
are multi-user, multi-programming and high-performance computers.
are large and powerful systems generally used in centralized databases.
Mainframe computers are used in organizations.
dumb terminal cannot store data or do processing of its own.
intelligent terminal has the input and output device, can do processing, but, cannot store data of its own.
The dumb and the intelligent terminal use the processing power and the storage facility of the mainframe
computer.
Supercomputers
are the fastest and the most expensive machines.
The speed of a supercomputer is generally measured in FLOPS (FLoating point Operations Per Second).
built by interconnecting thousands of processors that can work in parallel.
COMPUTER ARCHITECTURE
- refers to the structure and behavior of the computer.
- It includes the specifications of the components, for example, instruction format, instruction set and
techniques for addressing memory, and how they connect to the other components.
Computer organization
- focuses on the organizational structure.
- It deals with how the hardware components operate and the way they are connected to form the Computer.
Computer design
- focuses on the hardware to be used and the interconnection of parts.
2.2 Registers
Registers are high-speed storage areas within the CPU, but have the least storage capacity.
Registers are not referenced by their address, but are directly accessed and manipulated by the CPU during
instruction execution.
store data, instructions, addresses and intermediate results of processing.
often referred to as the CPU’s working memory.
used for different purposes, with each register serving a specific purpose.
Some of the important registers in CPU
1. Accumulator (ACC) stores the result of arithmetic and logic operations.
2. Instruction Register (IR) contains the current instruction most recently fetched.
3. Program Counter (PC) contains the address of next instruction to be processed.
4. Memory Address Register (MAR) contains the address of next location in the memory to be accessed.
5.Memory Buffer Register (MBR) temporarily stores data from memory or the data to be sent to memory.
6. Data Register (DR) stores the operands and any other data.
The number of registers and the size of each (number of bits)
The overall number of registers can vary from about ten to many hundreds, depending on the type and
complexity of the processor.
The size of register, also called word size, indicates the amount of data with which the computer can work at
any given time.
2.3 Control Unit
The control unit of a computer does not do any actual processing of data.
It organizes the processing of data and instructions.
It acts as a supervisor and, controls and coordinates the activity of the other units of computer.
coordinates the input and output devices of a computer.
uses the instructions in the Instruction Register (IR) to decide which circuit needs to be activated.
tells when to fetch the data and instructions, what to do, where to store the results, the sequencing of events
during processing etc.
also holds the CPU’s Instruction Set, which is a list of all operations that the CPU can perform.
When a program is run, the Program Counter (PC) register keeps track of the program instruction to be
executed next.
The function of a (CU) can be considered synonymous with that of a conductor of an orchestra. The
conductor in an orchestra does not perform any work by itself but manages the orchestra and ensures that
the members of orchestra work in proper coordination.
Lesson 3: MEMORY UNIT
The memory unit consists of cache memory and primary memory.
Primary memory or main memory of the computer is used to store the data and instructions during
execution of the instructions.
Random Access Memory (RAM) and Read Only Memory (ROM) are the primary memory.
there is another kind of storage device known as the secondary memory.
Secondary memory is non-volatile and is used for permanent storage of data and programs.
3.1 Cache Memory
The data and instructions that are required during the processing of data are brought from the secondary
storage devices and stored in the RAM.
it is required that the data and instructions are accessed from the RAM and stored in the registers.
Cache memory
- is a very high speed memory placed in between RAM and CPU.
- increases the speed of processing.
- a storage buffer that stores the data that is used more often temporarily, and makes them available to CPU at
a fast rate.
- is built into the processor, and may also be located next to it on a separate chip between the CPU and RAM.
To access the cache memory, CPU does not have to use the motherboard’s system bus for data transfer.
3.2 Primary Memory
Primary memory is the main memory of computer. It is used to store data and instructions during the processing of
data. Primary memory is semiconductor memory.
Primary memory is of two kinds—
1. Random Access Memory (RAM) and
2. Read Only Memory
RAM
- is volatile.
- It stores data when the computer is on. The information stored in RAM gets erased when the computer is
turned off.
- RAM provides temporary storage for data and instructions.
ROM
- is non-volatile memory, but is a read only memory.
- The storage in ROM is permanent in nature, and is used for storing standard processing programs that
permanently reside in the computer.
RAM stores data and instructions during the execution of instructions.
The input data that is entered using the input unit is stored in RAM
RAM provides a limited storage capacity, due to its high cost.
3.3 Secondary Memory
The secondary memory stores data and instructions permanently.
It provides back-up storage for data and instructions.
Secondary memory has a high storage capacity than the primary memory.
Secondary memory is also cheaper than the primary memory.
It takes longer time to access the data and instructions stored in secondary memory than in primary memory.
Lesson 4: INSTRUCTION FORMAT
- A computer program is a set of instructions that describe the steps to be performed for carrying out a
computational task.
- An instruction is designed to perform a task and is an elementary operation that the processor can
accomplish.
- An instruction is divided into groups called fields. The common fields of an instruction are— Operation (op)
code and Operand code.
The operation code represents action that the processor must execute.
The operand code defines the parameters of the action and depends on the operation.
- The number of bits in an instruction varies according to the type of data (could be between 8 and 32 bits).
Lesson 5: INSTRUCTION SET
- A processor has a set of instructions that it understands, called as instruction set.
- An instruction set or an instruction set architecture is a part of the computer architecture.
- It relates to programming, instructions, registers, addressing modes, memory architecture, etc.
- An Instruction Set is the set of all the basic operations that a processor can accomplish.
- The instructions in the instruction set are the language that a processor understands.
- The instruction set is embedded in the processor (hardwired), which determines the machine language for
the processor.
- Two processors are different if they have different instruction sets.
- Two processors are compatible if the same machine level program can run on both the processors.
Microarchitecture is the processor design technique used for implementing the Instruction Set.
Lesson 6: INSTRUCTION CYCLE
- The primary responsibility of a computer processor is to execute a sequential set of instructions that
constitute a program.
Four steps in an instruction cycle:
1. Fetching. The processor fetches the instruction from the memory. The fetched instruction is placed in the
Instruction Register. Program Counter holds the address of next instruction to be fetched and is incremented
after each fetch.
2. Decoding. The instruction that is fetched is broken down into parts or decoded. The instruction is translated
into commands so that they correspond to those in the CPU’s instruction set. The instruction set architecture of
the CPU defines the way in which an instruction is decoded.
3. Executing. The decoded instruction or the command is executed. CPU performs the operation implied by the
program instruction. For example, if it is an ADD instruction, addition is performed.
4. Storing. CPU writes back the results of execution, to the computer’s memory.
Lesson 7: MICROPROCESSOR
- A processor’s instruction set is a determining factor in its architecture.
- microprocessors are classified as—Reduced Instruction Set Computer (RISC), and Complex Instruction Set
Computer (CISC).
CISC architecture
- hardwires the processor with complex instructions, which are difficult to create otherwise using basic
instructions.
- CISC combines the different instructions into one single CPU.
- has a large instruction set that includes simple and fast instructions for performing basic tasks, as well as
complex instructions that correspond to statements in the high level language.
- Instructions are of variable lengths, using 8, 16 or 32 bits for storage.
- AMD and Cyrix are based on CISC.
RISC
- has simple, single-cycle instructions, which performs only basic instructions.
- RISC architecture does not have hardwired advanced functions.
- has fewer instructions and requires fewer transistors, which results in the reduced manufacturing cost of
processor.
- has a reduced production cost compared to CISC processors.
- The instructions, simple in nature, are executed in just one clock cycle, which speeds up the program
execution when compared to CISC processors.
- RISC processors can handle multiple instructions simultaneously by processing them in parallel.
- Apple Mac G3 and PowerPC are based on RISC.
External Bus connects the different external devices, peripherals, expansion slots, I/O ports and drive connections to
the rest of computer.
- Allows various devices to be attached to the computer.
- It allows for the expansion of computer’s capabilities.
- also referred to as the also referred to as the Expansion Bus.
• A system bus or expansion bus comprise of three kinds of buses — data bus, address bus and control bus.
• The interaction of CPU with memory and I/O devices involves all the three buses.
• The command to access the memory or the I/O device is carried by the control bus.
• The address of I/O device or memory is carried by the address bus.
• The data to be transferred is carried by the data bus.
Functions of data bus, address bus and control bus, in the system bus,
1. Functions Bus transfers data between the CPU and memory.
2. Address Bus connects CPU and RAM with set of wires similar to data bus.
3. Control Bus specifies whether data is to be read or to the memory, etc.
Functions of data bus, address bus and control bus, in the expansion bus:
1. The expansion bus connects external devices to the rest of computer. The external devices like monitor,
keyboard and printer connect to ports on the back of computer.
2. Expansion slots make up a row of long plastic connectors at the back of the computer with tiny copper ‘finger
slots’ in a narrow channel that grab the connectors on the expansion cards.
3. Data Bus is used to transfer data between I/O devices and CPU.
Some of the common bus technologies:
1. Peripheral Component Interconnect (PCI) bus for hard disks, sound cards, network cards and graphics cards.
2. Accelerated Graphics Port (AGP) bus for 3–D and full motion video, Universal Serial Bus (USB) to connect and
disconnect different devices.
3. Address Bus carries the addresses of different I/O devices to be accessed like the hard disk, CD ROM, etc.
4. Control Bus is used to carry read/write commands, status of I/O devices, etc.
External Ports
- The peripheral devices interact with the CPU of the computer via the bus.
- The different ports and sockets facilitate the connection of different devices to the computer.
Expansion Slots
The expansion slots are located on the motherboard.
The expansion cards are inserted in the expansion slots.
These cards give the computer new features or increased performance.
SEVERAL TYPES OF SLOTS:
1. ISA (Industry Standard Architecture) slot—To connect modem and input devices.
2. PCI (Peripheral Component InterConnect) slot—To connect audio, video and graphics. They are much faster than
ISA cards.
3. AGP (Accelerated Graphic Port) slot—A fast port for a graphics card.
4. PCI (Peripheral Component InterConnect) Express slot—Faster bus architecture than AGP and PCI buses.
5. PC Card—It is used in laptop computers. It includes Wi-Fi card, network card and external modem.
Ribbon Cables
Ribbon cables are flat, insulated and consist of several tiny wires molded together that carry data to different
components on the motherboard.
There is a wire for each bit of the word or byte and additional wires to coordinate the activity of moving
information.
They also connect the floppy drives, disk drives and CD-ROM drive to the connectors in the motherboard.
Serial Advanced Technology Attachment (SATA) replaced ribbon cables
Memory Chips
The RAM consists of chips on a small circuit board. Two types of memory chips— Single In-line Memory Module
(SIMM) and Dual In-line Memory Module (DIMM) are used in desktop computers.
Storage Devices
The disk drives are present inside the machine.
The common disk drives in a machine are hard disk drive, floppy) and CD drive or DVD drive.
Processor
The processor or the CPU is the main component of the computer.
Select a processor based on factors like its speed, performance, reliability and motherboard support.
AMD Ryzen series and Intel Core I series are some of the processors.