Extended Binary Coded Decimal Interchange Code (EBCDIC)
Is an 8-bit code scheme used to represent up to 256 xters. i.e. 2 8=256.
EBCDIC is mainly used in large IBM computers. E.g. A in EBCDIC is represented as
The 8th bit is used for parity check
BINARY ARITHMETIC OPERATIONS
In computing, Mathematical operations are performed in ALU. However, the ALU cannot perform the
binary subtractions directly. It performs it using complementation method.
For multiplication and division, the ALU uses the Shift
1) Differentiate between analogue data and digital data.
Analogue data_ a type of data that is continuous in nature.
Digital data - Data in discrete form.
2) Define the following terms
a) Amplitude: maximum vertical height attained by a wave
It involves dividing a processing task to two or more computers that are
located on physically separate sites but connected by a data transmission
Computers, software and data linked by common channels are dispersed
Extended Binary Coded Decimal (EBCD)
Is 6-bit coding scheme formed by adding a farther 2-bits in order to represent non-numeric xters.
This allows 64 xters to be represented. (26=64)
In the 6-bit coding scheme, the 2 additional bits are called zone bits a
BINARY NUMBER SYSTEM
A number system that consist of two digits i.e. 0s and 1s to represent data in a computer. These
numbers are written to the base of 2.
This number system is similar to decimal in that, the position of a digit in a number is influenced
ELECTRONIC DATA PROCESSING MODES
Data processing modes describe the ways in which a computer under the
influence of instructions by the operating system handle data during data
processing. These modes include:
Real time proc
CONVERTING HEXADECIMAL NUMBERS TO DECIMAL, BINARY AND OCTAL
a) Hexadecimal to Decimal
i) Write the place value starting from the right hand side.
ii) Write each digit under its place value. If a digit is a letter e.g. B, write its decimal
DECIMAL TO OCTAL
To convert from base 10 (denary) to octal (base8), the number in base 10 is repeatedly
divided by 8 until the dividend is zero.
On each division the remainder is noted.
Convert the following decimal number to octal equivalent.
American Standard Coded Decimal for Information Interchange (ASCII)
Is a 7-bit code scheme used to represent up to 128 xters. i.e. 2 7=128.
Since computers can only understand numbers, all xters must be represented by a number. i.e. the
ASCII numbers e.g
FILE ORGANIZATION METHODS
File Organization: Refers to the arrangements of records or how data is stored in a file. File
organization is important as it determines the method of access, efficiency, flexibility and storage
There are 4 methods
When discussing about operating system, we defined a file as an
organized collection of related information stored in a given storage
location and given a unique name for easier recall and access by the
computer whenever necessary.
CONVERTING OCTAL NUMBERS TO BINARY AND VICEVERSA
Here, each octal digit is represented by 3 binary digits.
A simple relationship exists between octal and binary because, 8 is the cube of 2.
The maximum octal digit i.e. 7 can be represented with a maximum
Definition of terms:
Data: Raw facts that do not have much meaning to the user. These include:
Figures, letters, symbols, xters etc.
Data cannot be used in decision making.
Information: Processed data that is meaningful to the user. Since
DATA COLLECTION (Gathering/ Fact finding)
It involves looking for or getting data from its point of origin to the computer
The methods involved for data collection include:
Sampling: Select repres
Is the accuracy, validity and completeness of data entered in a computer or
received from an information system.
Integrity of data is a major consideration when deciding a method of data
Integrity is measured/ assessed in the fo
CONCEPTS OF DATA REPRESENTATION IN DIGITAL COMPUTERS
Data and instructions cannot be entered and processed directly into computers using human
Any type of data must first be converted into machine readable form i.e. binary form.
A computer toget
TYPES OF DATA REPRESENTATION
1. NUMBER SYSTEMS
There are 4 main categories of number systems:
a) Decimal number system
b) Binary number systems
c) Octal number systems
d) Hexadecimal number systems
a) DECIMAL NUMBER SYSTEMS
Is a number system that has ten
a) Direct Subtraction
02-12=12 borrow 1
b) Ones Complement
For Example 510-310
i) Rewrite the problem as 5+(-3) to show that the computer performs binary subtractions
DATA PROCESSING METHODS
These are different ways in which an organization may decide to convert
(process) data collected over time to information.
Data can be processed :
1. Manual Data Processing
It involves the use o
2. DATA INPUT
Is the act of entering the collected data and instructions in a computer using
an input device.
The input data is converted from human readable form to machine readable
form (binary form).
3. DATA PROCESSING
Is the transformation of the inpu
Using Twos complement
It is achieved by getting ones complement of a number and then 1 is added. E.g
Find the twos complement of 4510
In 8 bits =001011012
The ones complement =110100102
Adding 1 t
DATA SECURITY THREATS AND CONTROL MEASURES
Information within the organization is the power of the organization and therefore the
information stored within the organization needs to be protected in order to maintain the integrity
of the organization.
DATA REPRESENTATION IN A COMPUTER
Data: Raw facts and figures that a computer processes by following a set of instructions called
programs. The way in which data is stored and represented depends on the medium storing it and the
type of data.
Types of dat
PRESENTING SIGNED BINARY NUMBERS (POSTIVE AND NEGATIVE) IN A
There are 3 ways of presenting signed numbers in a computer:
Prefixing an extra sign bit to a binary number.
Using ones complement
Using twos complement
Prefixing an extra sign bit
DECIMAL FRACTION TO BINARY
1. Multiply the fraction part by 2 and note down the product.
2. Take the fraction part of the immediate product and multiply it by 2 again.
3. Continue multiplying the fractional part by 2 until the subsequent product is 0 or s
TYPES OF COMPUTER PROCESSING FILES
There are several types of files used for storing data needed for
processing, reference or backup. These include:
Is the main file
B) DECIMAL TO BINARY
To convert a number from base 10 to base 2, the number in base ten is repeatedly divided by
two until the dividend is zero.
On each division the remainder is noted.
Remainders which are either 0 or 1 are written to the right of the qu
Hexadecimal to Octal
In this case, convert the hexadecimal number into binary equivalent and then convert the binary to
a) Convert BC216 to octal equivalent:
Convert BC216 to binary equivalent i.e.
CONVERSION OF NUMBERS FROM ONE SYSTEM TO ANOTHER
1. A) BINARY TO DECIMAL
i) Write the place value starting from right hand side.
ii) write each digit under its place value
iii) Multiply each digit by its corresponding place value.
iv) Sum up the products.