WAEC SSCE - Computer Studies - 2017 (Essay)

Bayanin Amsa

The three descriptions in the question have been shuffled. Each early electronic computer is matched to the description that historically belongs to it.

Reasoning:

• ENIAC (Electronic Numerical Integrator and Computer, 1945) was the first large-scale, electronic, general-purpose machine. It was reprogrammed by rewiring to carry out long, complex sequences of operations.
• EDVAC (Electronic Discrete Variable Automatic Computer, 1949) was the first widely known machine designed to work in binary, and it performed automatic addition, subtraction, multiplication and programmed division.
• UNIVAC (Universal Automatic Computer, 1951) was an electronic digital stored-program computer built for the U.S. Bureau of the Census, and later famous for predicting a presidential election result.

Bayanin Amsa

(a) One difference between star and bus topologies

In a star topology every computer is connected by its own cable to a central device (a hub or switch), so all data passes through that central point; if one cable fails only that one computer is affected. In a bus topology all computers are connected to a single common cable (the backbone), and if that main cable breaks the whole network goes down.

(b) Four common network devices

1. Hub.
2. Switch.
3. Router.
4. Modem. (Network interface card, bridge and repeater are also acceptable.)

(c) The acronyms in full

• HTML - HyperText Markup Language
• HTTP - HyperText Transfer Protocol
• ISP - Internet Service Provider
• SMTP - Simple Mail Transfer Protocol

Bayanin Amsa

(a) Convert \(1011011_2\) to hexadecimal

Method 1 (through denary):

\[1011011_2 = (1\times2^6)+(0\times2^5)+(1\times2^4)+(1\times2^3)+(0\times2^2)+(1\times2^1)+(1\times2^0)\]

\[= 64+0+16+8+0+2+1 = 91_{10}\]

Dividing 91 repeatedly by 16: \(91 = 5\times16 + 11\), where \(11 = \text{B}\). Reading the digits gives \(5\text{B}\).

Method 2 (direct grouping): group the bits in fours from the right, \(0101\;1011\). Then \(0101 = 5\) and \(1011 = \text{B}\).

Therefore \(1011011_2 = 5\text{B}_{16}\).

(b) One difference between a hacker and a scammer

A hacker is a person who uses backend technical knowledge of software to gain unauthorised access to the computer systems or accounts of unsuspecting users, with the aim of stealing, altering or exploiting data. A scammer deceives victims through confidence tricks, sending unwanted or inappropriate electronic messages to many recipients, or luring the victim into granting remote access, in order to defraud them. In short, the hacker breaks in through technical means, while the scammer relies on deception to make the victim hand over money or information.

(c) Parts labelled A, B, C and D on the keyboard

• A - Function keys (F1 to F12), the row along the top.
• B - Alphanumeric (typing) keys, the central QWERTY block of letters, numbers and symbols.
• C - Numeric keypad, the calculator-style block of number keys on the right.
• D - Cursor (arrow) control keys, used to move the pointer up, down, left and right.

Bayanin Amsa

(a) Convert \(1011011_2\) to hexadecimal

Method 1 (through denary):

\[1011011_2 = (1\times2^6)+(0\times2^5)+(1\times2^4)+(1\times2^3)+(0\times2^2)+(1\times2^1)+(1\times2^0)\]

\[= 64+0+16+8+0+2+1 = 91_{10}\]

Dividing 91 repeatedly by 16: \(91 = 5\times16 + 11\), where \(11 = \text{B}\). Reading the digits gives \(5\text{B}\).

Method 2 (direct grouping): group the bits in fours from the right, \(0101\;1011\). Then \(0101 = 5\) and \(1011 = \text{B}\).

Therefore \(1011011_2 = 5\text{B}_{16}\).

(b) One difference between a hacker and a scammer

A hacker is a person who uses backend technical knowledge of software to gain unauthorised access to the computer systems or accounts of unsuspecting users, with the aim of stealing, altering or exploiting data. A scammer deceives victims through confidence tricks, sending unwanted or inappropriate electronic messages to many recipients, or luring the victim into granting remote access, in order to defraud them. In short, the hacker breaks in through technical means, while the scammer relies on deception to make the victim hand over money or information.

(c) Parts labelled A, B, C and D on the keyboard

• A - Function keys (F1 to F12), the row along the top.
• B - Alphanumeric (typing) keys, the central QWERTY block of letters, numbers and symbols.
• C - Numeric keypad, the calculator-style block of number keys on the right.
• D - Cursor (arrow) control keys, used to move the pointer up, down, left and right.

Bayanin Amsa

(a) What are input devices?

Input devices are hardware devices (peripherals) connected to a computer that are used to enter data, instructions, commands or signals into the computer system for processing. They allow the user to interact with and control the computer.

(b) Two input devices

1. Keyboard
2. Mouse

(Scanner, joystick, microphone, light pen, webcam, barcode reader and fingerprint scanner are also acceptable.)

(c) Two uses of logic gates

1. They serve as the building blocks of digital electronic circuits, used to construct the Arithmetic and Logic Unit (ALU), adders and memory cells inside the processor.
2. They are used as decision-making elements in control circuits such as burglar alarms, traffic-light controllers and automatic push-button lock circuits.

(d) Logic gate symbols

(i) OR gate – the output is 1 when at least one of the inputs A or B is 1.

(ii) AND gate – the output is 1 only when both inputs A and B are 1.

Bayanin Amsa

(a) Two differences between RAM and ROM

(b) Four characteristics of the Windows operating system environment

1. It has a Graphical User Interface (GUI) with icons, menus and windows.
2. It is multi-tasking - it can run several programs at the same time.
3. It is mainly mouse (pointer) driven, with point-and-click and drag-and-drop operations.
4. It uses a desktop with a taskbar and Start menu, and supports plug-and-play devices. (WYSIWYG display is also acceptable.)

(c) Two examples of utility programs

1. Antivirus program.
2. Disk defragmenter (or a file-compression / backup program).