Chapter 2 Comp Sci

In an 8-bit register, state the binary representation of the hexadecimal number 3B. [2]

00111011;

. Calculate how many different colours can be represented using two hexadecimal characters. [2]

2 hex = 4 + 4 = 8 bits; hence 256 colours;

4. Colours are represented by a computer as a combination of the three primary colours: red, green and blue. Numerical values are used to represent the different shades of each primary colour. These values range from 0 to 255 in decimal, or 00 to FF in hexadecimal. (b) State the number of bits used to represent a non-primary colour, such as yellow. [1]

24;

State how many integers could be represented in this byte. [1]

256;

4. Colours are represented by a computer as a combination of the three primary colours: red, green and blue. Numerical values are used to represent the different shades of each primary colour. These values range from 0 to 255 in decimal, or 00 to FF in hexadecimal. (c) State the maximum number of colours that can be represented in a computer pixel. [1]

2^24

(i) State how the data stored in the following byte will be represented in hexadecimal. [1] 0 1 0 1 1 1 1 0

5E;

Construct a truth table for the following Boolean expression. (A and B) nor C [3]

A B C. (A and B) nor C 0. 0. 0. 1 0. 0. 1. 0 0. 1. 0. 1 0. 1. 1. 0 1 0. 0. 1 1. 0. 1. 0 1 1. 0. 0 1. 1. 1. 0

Construct a truth table for the following Boolean expression. (A or B) and (not C or B) [4]

A B C. (A or B) and (not C or B) 0. 0. 0. 0 0. 0. 1. 0 0. 1. 0. 1 0. 1. 1. 1 1 0. 0. 1 1. 0. 1. 0 1 1. 0. 1 1. 1. 1. 1

Construct the truth table for the following expression. A xor (B or C) [3]

A B C. A xor (B or C) 0. 0. 0. 0 0. 0. 1. 1 0. 1. 0. 1 0. 1. 1. 1 1 0. 0. 1 1. 0. 1. 0 1 1. 0. 0 1. 1. 1. 0

Construct a truth table for the Boolean expression not (A xor B) and C. Use the following headings in your table. A. B. C. A xor B. NOT (A xor B). NOT(A xor B) AND C

A B C. A xor B. NOT(A xor B). NOT(AxorB) and C 0. 0. 0. 0. 1 0 0. 0. 1. 0 1 1 0. 1. 0. 1 0 0 0. 1. 1. 1 0 0 1 0. 0. 1 0 0 1. 0. 1. 1. 0 0 1 1. 0. 0 1 0 1. 1. 1. 0. 1 1

Outline how a colour can be represented in a computer. [2]

A colour will be split into three components; Each componentwill be assigned a certain number of bytes;

(ii) Outline the function of an operating system in managing primary memory. [2]

A part of the OS assigns that block of memory to the program when a running program requests a block of memory;When the program no longer needs the data in previously allocated memory blocks, they become available for reassignment;

Define the term peripheral. [1]

A peripheral is an external device that is connected to a computer such as a keyboard;

Define the term operating system. [1]

A set of programs through which a computer manages its own resources;

Construct a truth table with two input variables. If input variables are equal the value of output variable should be True, False otherwise. [2]

A(0011)B(0101)C(1001)

Construct the truth table for the following Boolean expression. X = not A and B or A and not B [4]

A. B. X T. T. F F. T. T T. F. T F. F. T

State the part of the central processing unit (CPU) that is responsible for carrying out calculations. [1]

Arithmetic and ALU;

Explain the importance of the memory management function of an operating system. [3]

Assigns blocks of memory to programs; Manages virtual memory if needed; To avoid overwriting /clashing of programs/optimise system performance/maximise memory usage

Construct a logic diagram for the following expression. not A or (A and B) [3]

Award [1] for a logic diagram representing A OR B with 2 inputs, 1 output and 3 logicgates.Award [1] for the OR gate having 2 inputs, one of which is NOT A.Award [1] for another input to the OR gate, which is A AND B.

Define the term bit. [1]

Binary digit;

Outline the relationship between binary an· d hexadecimal. [2]

Binary numbers have base 2, hexadecimal numbers have base 16; Each digit in a hexadecimal number can be represented by the group of four binary digits;

The machine instruction cycle is the process by which a program instruction is fetched, decoded, executed and the results are stored. (b) Outline the role of the data bus and address bus in this process. [2]

Buses are used as physical connections to carry information to the CPU; The data bus transports data from CPU, whereas the address bus the memory address where the data is supposed to go;

Describe how the cache memory can speed up the functioning of a processor. [2]

By holding frequently used data and instructions in cache; Execution of program instructions and data is faster;

. Explain why cache memory can speed up the processing within a computer. [2]

Cache memory can be accessed faster than RAM; It is used to hold common used data;

(b) Explain the purpose of cache memory. [3]

Cache memory is a memory that a computer microprocessor can access more quickly than it can access regular RAM;It is integrated directly with the CPU chip or placed on a separate chip which has a separate bus interconnect with the CPU; and stores frequently used data only until a computer is powered down;

Construct a logic diagram for the following Boolean expression. NOT A OR (A AND B) [3]

Clearly a logic diagram with 2 inputs, 1 output and 3 logic gates[1];ORgate has two inputsone of which is NOT A [1] and the other is A AND B [1]

State the hexadecimal equivalent of the following binary number: 11011111 [1]

DF;

(a) Outline what is meant by a database management system. [2]

Database management system is an application software;that allows users to define a database / provides (controlled) access to the data;

(b) Distinguish between fundamental and compound operations of a computer. [2]

Fundamental operation requires one machine instruction cycle/do not require the processor to go through many machine instruction cycles to reach a result; A compound operation is complex / it is an operation that involves a number of other operations to reach the result; For example, find the largest number in an array/ sort the array in ascending order etc;

4. Colours are represented by a computer as a combination of the three primary colours: red, green and blue. Numerical values are used to represent the different shades of each primary colour. These values range from 0 to 255 in decimal, or 00 to FF in hexadecimal. (a) State why hexadecimal numbers are frequently used in computing. [1]

Hexadecimal numbers are used for shorter representation of data because a byte can be represented exactly by two hexadecimal digits;

Outline the role of the memory data register in the machine execution cycle. [2]

Holds the contents of the memory; Which are to be transferred from memory to other CPU components;

(a) State the purpose of cache memory. [1]

Is used to save time in accessing RAM;

(a) State the function of the control unit (CU) in the central processing unit (CPU). [1]

It decodes the instructions and controls all the other internal components of the CPU to make it work;

Outline two characteristics of spreadsheets. [2]

Made up of rows and columns used to organize data; Automatically calculates results when data is entered;

Explain two functions that an operating system needs to perform in relation to multitasking. [4]

Memory management; By allocating separate memory to each program; Processor Management; By the allocation of time slices;

Outline one feature of the operating system that needs to be considered when running a game application. [2]

Memory management; Game applications use a lot of memory and require constant refreshing;

Identify two features of a graphical user interface (GUI). [2]

Menus and dialogue boxes

Describe the function of the control unit (CU) in the central processing unit (CPU). [2]

Obtains the data from the memory; Interprets them into commands;

. Outline the function of the ALU. [1]

Part of a processor that performs arithmetic and logical operations;

Outline the function of the (a) ALU; [1]

Part of a processor that performs arithmetic and logical operations;

Outline the Function of the (b) CU. [1]

Part of processor which coordinates all activities in processor and all other parts within a computer;

Draw a diagram to show the relationship between random access memory (RAM), the processor and cache memory. [1]

Processor --> Cache --> Ram

The machine instruction cycle is the process by which a program instruction is fetched, decoded, executed and the results are stored. (a) State where all instructions and data are stored. [1]

RAM

(a) (i) Distinguish between random access memory (RAM) and read only memory (ROM). [3]

RAM acts as temporary storage of data, instructions and programs currently running whilst ROM is permanent memory (stores the instructions and data that won't change/stores the instructions that the computer needs in order to boot up; Memory access, both read and write operations are performed on RAM whilst ROM works with read only operation; If power failures happened during access to RAM then all data will be permanently lost/RAM is volatile memory/whilst if power failure happened during the ROM access no data will be lost/ROM is non-volatile memory;

14. A company that provides training for teachers plans to set up a training room in its offices with a network of 15 computers. Each computer has 1 TB of storage and 16 GB of random access memory (RAM). (a) Identify two characteristics of RAM. [2]

RAM is volatile erased when power is switched off;Access speed is fast than hard drive;

Distinguish between the uses of two types of primary memory. [2]

RAM stores data and instructions currently in use ROM stores permanent instructions Cache stores frequently used instructions

(a) Identify one fundamental operation of a computer. [1]

Retrieve

14. A company that provides training for teachers plans to set up a training room in its offices with a network of 15 computers. Each computer has 1 TB of storage and 16 GB of random access memory (RAM). (c) Identify two types of general application software that would be installed on the training computers. [2]

Spreadsheet;Database management system;

Outline, with an example, one benefit of using computer-aided design (CAD) applications.

Support design prototyping in engineering; Save time associated to development;

Outline the purpose of the memory address register (MAR) in the central processing unit (CPU). [2]

The MAR holds the memory location of data that need to be accessed.

Outline the purpose of the memory address register (MAR) in the central processing unit (CPU). [2]

The MAR holds the memory location of data/instructions;...that need to be accessed (read/write) (fetch/store);

One of the functions of an operating system is memory management. Describe how this function prevents the system from crashing when more than one program is run at the same time. [2]

The OS allocates specific sections of memory to each program; This ensures that the memory assigned to one program is not overwritten;

Outline why this byte could not be used to represent characters such as those used in Chinese. [2]

The characters must be represented as numbers so that computer can deal with them; Chinese exceeds the 256 character limit and therefore requires more bytes to represent all of the characters in this language;

14. A company that provides training for teachers plans to set up a training room in its offices with a network of 15 computers. Each computer has 1 TB of storage and 16 GB of random access memory (RAM). (b) State the purpose of persistent storage on the computers. [1] In order to minimize costs, the company decided only to install general application software on the training computers. ]

To store programs in a non-volatile device so it isn't lost;

Harry is tired (T) depending on the following 3 variables - Work (W) - Hungry (H) - Sun (s) Harry is tired if he - If he works and he is hungry - He works and it is not sunny - Does not work and is not hungry b. Construct the truth table to show when Harry is tired [4]

W H S T 0 0 0 1 0 0 1 1 0 1. 0 0 0 1. 1. 0 1 0. 0. 1 1 0. 1. 0 1 1. 0. 1 1. 1 . 1. 1

Harry is tired (T) depending on the following 3 variables - Work (W) - Hungry (H) - Sun (s) Harry is tired if he - If he works and he is hungry - He works and it is not sunny - Does not work and is not hungry a. Represent, as a single logical operation, the conditions that cause Harry to be tired. [3]

W* H + W * -S + -W * -H Alternative equivalent solution:W*(H+-S) + -W*-H

Explain the roles of the data bus and the address bus in the machine instruction cycle. [4]

When the computer processor needs to fetch an instruction from the memory it uses the address bus to specify the address; It will get the data from memory;