Section 1: Fundamentals of Hardware and Software Flashcards
The major functions of a general-purpose system are:
Input: involves obtaining data for processing
Processing: involves the manipulation of data to produce information. Manipulation means multiplying, adding, subtracting, dividing, sorting etc.
Output: involves sending information to users.
Storage: involves keeping the data on electronic storage.
What is the Central Processing Unit (CPU)?
The CPU is also called the processor. It takes raw data, follows a set of instructions (programs) and converts it into information. The CPU consists of two smaller units known as the control unit (CU) and the arithmetic and logic unit (ALU).
What is the Control Unit (CU)?
This is the main part of the CPU. It directs and coordinates all activities within the CPU. It determines the sequence in which instructions are executed. The CU executes an instruction by performing the following steps:
- Fetching the instructions from memory
- Decoding the instructions
- Fetching the data required by the instructions from memory
- Sending the data and instructions to the ALU for processing
- Sending the data to memory after processing
What is the Arithmetic and Logic Unit (ALU)?
The ALU performs all the arithmetic and logic functions in a computer. The arithmetic operations include addition (+), subtraction (-), multiplication (*) and division (/).
What is the Main Memory?
Main memory is also called computer memory, immediate access storage (IMAS/IAS) or primary storage. This unit of memory is directly accessible to the CPU. It holds data and instructions that the computer is processing at the time.
What is the Secondary Storage?
These devices are used to store data and instructions when they are not being processed. Secondary storage is more permanent than main memory, since data and instructions are not lost when the power is turned off. It is also much cheaper than primary storage and is unlimited since you can have as much of it as you can afford. The most commonly used auxiliary storage devices are magnetic storage (tapes and disks), optical storage (CD ROM, CD-R, DVD-ROM, DVD-R and DVD-RW and solid state memory (flash memory and USB drives).
What are Peripheral Devices?
Peripheral devices are any device controlled or monitored by the CPU. It includes both input and output devices.
What are Input Devices?
Input devices are any device that is used to put data and instructions into the computer. Some commonly used input devices are keyboard, mouse, joystick, digital camera, scanners, barcode readers and magnetic strips.
What are Output Devices?
Output devices are any device that is used to get information out of a computer. Some commonly used output devices are VDU or monitor, printer, plotter, speakers and multimedia projector.
What is the Primary Storage?
This is a group of silicon chips that resides on the computer’s motherboard (main circuit board). Primary storage consists of two types of memory chips: RAM and ROM chips. A memory chip is an integrated circuit (IC) made up of millions of transistors and capacitors.
What is RAM?
Random Access Memory is a chip that is used to hold data and instructions (programs) temporarily while processing is taking place using that data and program. It also holds the data that results from processing – data that is waiting to be output or stored in a secondary storage device. RAM is volatile i.e. it is temporary and changeable. If the power is turned off or the computer is rebooted (started up again) all the information held in RAM will be lost.
What is ROM?
Read Only Memory is a chip that holds data and instructions necessary for starting up the computer when it is switched on. It is used to store system-level programs such as the BIOS (Basic Input Output System) program.
What are the Variations of ROM?
Programmable ROM (PROM) : This type of ROM can be programmed only once using special equipment. It is useful for companies that want to make their own ROMs from software they write themselves. If they change their code they can create new PROMs without requiring a ROM manufacturer.
Erasable programmable ROM (EPROM) : This type of ROM can be erased and reprogrammed, which makes it more useful than a PROM. EPROM chips are programmed in the same way as PROM chips. Data is erased from this chip by exposing it to ultraviolet light of a specific frequency for a specified period of time.
What are Units of Storage?
Memory is made up of bistable devices. Bistable means the components that make up memory can be set to one of two states either on or off. These two states are represented using binary digits- 0 for off and 1 for on. As such, the smallest unit of storage of memory is called a binary digit (bit). The amount of data and instructions that can be stored in primary storage or secondary storage media is measured in bytes.
What is a byte?
A byte is made up of a combination of 8 bits and has the capacity to represent one character i.e. a letter, a number, a symbol, a punctuation mark or a blank space.
What is a Word?
A word is the amount of bits the computer can process in one operation.
What is a Word size?
A word size or word length is the number of bits in a word.
Larger Units of Storage
- Kilobyte
- Megabyte
- Gigabyte
- Terabyte
- Petabyte
- Exabyte
- Zettabyte
- Yottabyte
Secondary Storage Media
Secondary storage devices are chosen for a particular use based on their:
- Storage capacity (how much data the device can store)
- Access speed ( the time needed to locate the data and transmit it to the CPU)
- Portability ( ability to be easily removed and used on another system)
- Cost
- Size (necessary for storage on shelves or portability)
Magnetic tape
A magnetic tape looks like an audiocassette tape. Tapes may come in different sizes. It is used mainly to backup hard disks because it can store large amounts of data at a low cost. Accessing data on a tape is very slow since data is stored sequentially. Sequentially means that data is retrieved in the order which it was stored.
Magnetic disks (Floppy disk, Hard disk)
All magnetic disks provide direct access to stored data. This means that you can go directly to specific piece of data without having to access any other either before or after the data you want.
Floppy disk
This is also called a diskette. It is a removable, flexible plastic disk, coated with a magnetisable material. The floppy disk is used to store and transfer small amounts of data between computers. Data and information is written to or read from the disk by a read/write head in the disk drive held in the system unit. Data is stored on both sides of a diskette on tracks and sectors. Before data is stored on a floppy disk, it needs to be formatted. Formatting means writing electronic information on the disk so that the computer can recognize the disk as a valid storage device where data can be stored.