ICT (Computer Studies) - xpino SCHOLARS

A work tool for teachers and students, but especially for Secondary School Students. Comprehensive lesson notes, with exercises. Past questions in specific subjects for revision and research.

Saturday, December 27, 2014

ICT (Computer Studies)

A computer may be defined as a machine that can solve problems by accepting data, performing certain operations and presenting the results of those operations under the direction of detailed step-by-step instructions.

Constituents of a Computer
A computer consists of hardware and software. Description: C:\Users\XpinoLogistics\Desktop\sony_rm1n_1.jpg        The hardware is the physical part of the computer that can be seen and touched.
The basic set of hardware found in most PCs are:
1.      PC Case
2.      Motherboard
3.      Power Supply
4.      Hard Disk Drive (HDD)
5.      Floppy Disk Drive (FDD)
6.      Compact Disk Drive (CDD)
7.      Digital Video Disk Drive (DVD)
8.      Monitors (CRT and LCD)
9.      Keyboard
10. Mouse
11. Audio
12. Cables and wires.

Hardware can be broadly divided into two parts namely: System Unit and Peripherals.
·         System Unit or Computer case is the part of a computer that houses the primary devices that perform operations and produce results for complex calculations. It includes the motherboard, CPU, RAM and other components, as well as the case in which these devices are housed.
           Description: C:\Users\XpinoLogistics\Desktop\system05.png
·         Peripherals are devices that are used to put information into or get information out of a computer. Some types of peripherals are: Description: C:\Users\XpinoLogistics\Desktop\peripherals2.gif
a.     Input devices (mouse, keyboards etc.)
b.     Output devices (monitors, printers etc.)
c.     Storage devices (hard drives, flash drives, etc.)

1.      What is a computer?
2.      What are the two main components of a computer?
3.      What is hardware?
4.      What are seven examples of computer hardware components?
5.      What are the differences between system unit and peripherals?

1.      What is CPU?
2.      What is the purpose of the CPU?
3.      Who made the world first CPU? In what year?
4.      What is Intel 8008?


   Description: C:\Users\XpinoLogistics\Desktop\url.bmp 
The purpose of the CPU is to process data. The CPU is the brain of the computer where most calculations take place. In term of computing power, the CPU is the most important element of a computer system.
The world’s first CPU was introduced by Intel in 1971. It was known as Intel 4004. Five months later after the Intel 4004, the Intel 8008 was introduced. This was the world’s first 8-bit microprocessor.
The CPU itself is an internal component of the computer. Modern CPUs are small and square and contain multiple metallic connectors or pins on the underside. The CPU is inserted directly into a CPU socket, pin side down, on the motherboard.
Each motherboard will support only a specific type (or range) of CPU, so check must be made to ascertain the motherboard manufacturer’s specifications before attempting to replace or upgrade a CPU in your computer. Modern CPUs also have an attached heat sink and small fan that go directly on top of the CPU to help dissipate heat.

The two typical components of a CPU:
1.      Arithmetic logic unit (ALU) contains the electronic circuitry that performs arithmetic and logical operations.
2.      Control Unit (CU) communicates with both the arithmetic/logic unit and memory. It extracts instructions from memory, decodes then executes them, calling on the ALU when necessary.

Main Design of CPU
CPU is a complex design which comprises many hardware components like motherboard and circuits. The CPU works by receiving set of instructions, logic gates are used to execute and follow the set of instruction. This set of instruction is commonly known as a programme.
The early design of the CPU allowed only numerals and decimal system to represent the numbers. However, the design of the modern CPUs allows them to present numbers in binary form.

1.      The ALU helps the CPU to perfume calculations and take logical decisions.
2.      The CPU interacts closely with primary storage, or main memory, referring to it for both instructions and data.
3.      Technically, memory is not a part of the CPU.

Working of Control Unit
1.      The control unit directs the entire computer system to carry out stored program instructions.
2.      The control unit must communicate with both the arithmetic logic unit and main memory.
3.      The control unit uses the instruction contained in the Instruction Register to decide which circuits need to be activated.
4.      The control unit instructs the arithmetic logic unit which arithmetic operations or logic operation is to be performed.
5.      The control unit is literally in control.

Working of ALU
1.      The arithmetic and logic unit executes arithmetic and logic operations.
2.      Arithmetic operations include addition, subtraction, multiplication and division.
3.      Logical operations compare numbers, letters and special characters.
4.      Relational operations (=, <,>) are used to describe the comparison operations used by the arithmetic logic unit.
5.      The arithmetic logic unit performs logic functions such as AND, OR and NOT.
6.      Comparison operations test for three conditions: 
(a) equal-to condition in which two values are the same;
(b) less-than condition in which one value is smaller than the other;
(c) greater-than condition in which one value is larger than the other.

1.      What is CPU?
2.      What is the purpose of the CPU?
3.      Who made the world first CPU? In what year?
4.      What is Intel 8008?
5.      What is the difference between the world first CPU and the modern CPU?
6.      What must you check before attempting to replace or upgrade a CPU in your computer?
7.      Why do Modern CPUs have heat sink and small fan attached to them?
8.      What are the five differences between ALU and CU?
9.      Which CPU design uses binary form, early design or modern design?

1.      Why is memory not part of a CPU?
2.      What is the full meaning of RAM?

Memory is also known as primary storage, primary memory, main storage, internal storage, main memory and RAM (Random Access Memory)
By definition, memory is the part of the computer that holds data and instructions for processing.
Although closely related associated with the CPU, memory is separate from it. The Memory stores program instructions or data for only as long as the program they pertain to is in operation.
A memory is just like a human brain. It is used to store data and instruction. Computer memory is the storage space in computer where data is to be processed and instructions required for processing are stored.
The main characteristic of memory is that it allows very fast access to instructions and data, no matter where the items are within it. The Memory uses the Binary concept for storage.

The Binary Concept
Computers can’t understand our language and can understand only their language. The computer language is called BINARY. The binary is made up of a combination of 0s and 1s only.
Due to the fact that computer only understand binary, a special coding technique had to be formed so that the numbers, letters and other characters could be converted into a computer understandable format.

Memory Measurement
Binary system is a base 2 system with only 2 digits 0 and 1. It occupies one space in memory. This one unit is known as a bit, a binary digit. A bit is a single binary value 1 or 0. A grouping of 8 bits is a byte. The bite is used as the basic unit for measuring size of memory, although with today’s memory sizes, it is more common to hear the term kilobyte (KB) or megabyte (MB) or Gigabyte (GB)
            8 bits                           = 1 byte
            1 kilobyte                  = 1024 bytes
            1 Megabyte                        = 1024 kilobytes
            1 Gigabyte              = 1024 Megabyte
            1 Terabyte                = 1024 Gigabytes

Note: Nibble is half of an eight-bit byte – four bits. Nibbles are important in hexadecimal representations.

Types of Computer Memory
There are two main types of computer memory, namely:
1.      Primary memory and
2.      Secondary memory

Primary Memory
This is the memory that can be directly accessed by the CPU which constantly interacts with it, retrieves data stored therein, goes through instructions and execute them as per the requirement.
The main part of the temporary memory is the Random Access Memory (RAM). The ram is a temporary but fast form of memory. Apart from the RAM the Processor Registers and the Processor Cache are parts of the primary memory. 

It is on the processor register that the CPU instructs and helps the Arithmetic and logic unit to perform a number of calculations.

Processor cache enhances the performance of the computer and links the fast registers to the slower main memory.

The primary memory also consists of the Read Only Memory (ROM). The ROM retains the stored data when the power supply is cut out. The ROM chip can only be read. It does not accept any input data or instructions from the users.

Exercises/Class activity:
1.      Fill the blank spaces in the paragraph below:
____________  is the part of the computer that holds data and instructions for processing. The computer language is called ___________.  A grouping of 8 bits is a ________.  Nibbles are important in ______________ representations. The main part of the temporary memory is the __________________________.  The four main parts of the primary memory are ___________________, ___________________, __________________________ and ___________________.  The ________ chip can only be read. The non-volatile memory that is stored externally to the computer is called ____________ memory. ________________________ enhances the performance of the computer and links the fast registers to the slower main memory.
2.      What is memory?
3.      What is primary memory?
4.      What does the computer memory do?
5.      What is the main characteristic of a computer memory?
6.      What is the binary concept?
7.      What is a bit?
8.      What is a byte?
9.      What is a kilobyte?
10.  What is a megabyte?
11.  What is a gigabyte?
12.  What is a terabyte?
13.  What is a nibble?
14.  How many megabytes make a gigabyte?

Write the full meaning of the following:
a.     RAM
b.     ROM
c.     KB
d.     GB
e.     MB
f.        CD
g.     CD-ROM
h.     CD-R
i.         CD-RW
j.         DVD

Types of Secondary Memory
Secondary Memory is the non-volatile memory that is stored externally to the computer. A secondary-storage medium is usually used for the storage of large amounts of data or for permanent or long-term storage of data or programs.
Secondary Memory is also used for storing backups, or copies of data and program so that they are not permanently lost if primary-storage power is interrupted.

Types of secondary memory:
1.      Magnetic: This is a Myler or metallic platter on which electronic data are stored. The data are recorded as tiny invisible magnetic spots on its oxide coating. Examples are:
·         Magnetic Tape
·         Magnetic disk
·         Hard disks
·         Floppy disks

2.      Optical: this technology involves the use of laser beams – highly concentrated beams of light. Examples are:
·         Optical disk
§  CD
§  DVD
§  Optical card
§  Optical tape
3.      Electronic
·         Flash Memory
4.      Other
·         Punched Card

The following table summarizes the characteristics of the various kinds of data storage in the storage hierarchy…
Relative Cost
Very fast
Floppy Disk
Very slow
Hard Disk
Very high

·         Floppy is 1.44MB in size; available in 2 sizes - 5¼’’  and 3½’’.
·         CD-ROM has the capacity of about 1000 floppies – 650MB. It is 4.72inches in size.
·         DVD can store at very large capacity. It is 12cm in size. It stores 7 times more data than CD-ROM.
·         Flash drive is small in size. It can store more that 1GB, relatively expensive.
·         Combo drive means a combination of CD-RW and DVD.

1.       What is secondary memory?
2.       What is a combo drive in respect to secondary memory?
3.       What can secondary memory be used for?
4.       What are three examples of secondary memory devices?
5.       What is the difference between a CD and a DVD?
6.       What is the difference between a RAM and a Hard disk?

What are two differences between a primary and secondary memory?

Differences between Primary and Secondary Memory
The memory hierarchy is very crucial operation functionality in the computer and can be categorized into primary and secondary memory. Both these memories vary in the speed, cost and capacity.

Primary memory is considered as a main memory that is accessed directly by the computer, so as to store and retrieve information.

Secondary memory is considered as an external or additional memory, this memory is not directly accessed by the CPU because, the secondary memory is an external storage device, It can be used as a permanent memory, because even when the computer is turned off we can retrieve the information.

Processor access the primary memory in a random fashion. Unlike primary memory, secondary memory is not directly accessed through CPU. The accessing of the primary memory through CPU is done by making use of address and data buses, whereas input/ output channels are used to access the secondary memory.

The primary memory is embedded with two types of memory technologies; they are the RAM (Random Access Memory) and ROM (Read Only Memory) while the secondary memory is accessible in the form of Mass storage devices such as hard disk, memory chips, Pen drive, floppy disk storage media, CD and DVD.

    Primary memory is volatile in nature, while secondary memory is non-volatile. The information that is stored in the primary memory cannot be retained when the power is turned off. In case of secondary memory, the information can be retrieved even if the power is turned off because the data will not be destructed until and unless the user erases it.
When the data processing speed is compared between the primary and secondary memory, the primary memory is much faster than the secondary memory.

In the cost perspective, the primary memory is costlier than the secondary memory devices. Because of this reasons most of the computer users install smaller primary memory and larger secondary memory.
As the secondary memory is permanent, all the files and programs are stored in the secondary memory most. As the primary memory interacts very fast with the micro-processor, when the computer needs to access the files that are stored in the secondary memory such files are first loaded into the primary memory and then accessed by the computer.


·         Primary memory is the main memory (Hard disk, RAM) where the operating system resides.
·         Secondary memory can be external devices like CD, floppy magnetic discs etc. secondary storage cannot be directly accessed by the CPU and is also external memory storage.
·         Primary memory storages are temporary; whereas the secondary storage is permanent.
·         Primary memory is expensive and smaller, whereas secondary memory is cheaper and larger.
·         Primary memory storages are faster, whereas secondary storages are slower.
·         Primary memory storages are connected through data buses to CPU, whereas the secondary storages are connect through data cables to CPU.
·         Commonly used primary memory (main memory) available in the range of 512 MB to 8 GB RAMs. However, secondary memories range between 80 GB to 4 TB Hard Disc Drives.
·         The primary memory devices are connected to the computer through “slots”        

1.      How can you categorize the computer memory hierarchy?
2.      What is primary memory?
3.      What is secondary memory?
4.      How do you access the primary memory through CPU?
5.      Why do we say primary memory is volatile?
6.      Why do we say secondary memory is volatile?
7.      What are five major differences between primary and secondary memory types?

1.      What is a Logic gate?
2.      What are the three basic logic gates?

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