140 Computing A-Level Revision Questions

        i)        immediate

        ii)        direct

        iii)        indirect

64. Describe the difference between a one address and a two address system for machine code instructions when implementing a simple arithmetic operation.
65. Name the registers associated with the Fetch/execute cycle
66. Describe the steps carried out when the following instructions are executed:

i)        MUL A

ii)        JSR 400

67. Convert to decimal (binary values are in twos complement and use 8 bits):

i)        0110 0011

ii)        1001 1001

iii)        1100 0111

68. Convert these binary numbers to hexadecimal

i)        1000 0110

ii)        1001 1100

iii)        1111 1110 0111 0000

69. Explain, with examples how numbers are represented in twos complement.
70. Explain normalisation of floating point numbers and why it is used.
71. A computer uses a 12-bit word. Numbers are in normalised floating point form with 8 bits for the mantissa and 4 bits for the exponent. Twos complement is used for both parts.

What decimal numbers do the following represent:

i)        01100101 0011

ii)        10100011 0100

72. Perform the following subtraction using the twos complement method, showing all working:

72.25 - 38.75  (use a 12-bit word and fixed point format with 8 bits before the point)

73. What are the two features of Assembly languages which make them easier to use than machine code?
74. What are the advantages of high level languages over assembly code?
75. State two advantages of low level languages over high level languages?
76. A stock control system uses batch processing. State 6 items of data which the Master File might contain. State the items of data needed in the Transaction File for each stock record.
77. Explain block packing density and cylinder packing density with reference to the creation of indexed sequential and direct access files.
78. Suggest, with reasons, a method of processing for each of the following applications (in some cases more than one might be used):

        payroll

        stock control          

        airline reservations

        insurance company

        banking

        library borrowers' file

        library book catalogue

79. Explain the difference between a serial and a sequential file. For what use is a serial file organisation commonly used?
80. Describe the data structure known as a linked list and say how it may be implemented in programming. Suggest uses for this structure.
81. State five methods of accessing data from a table in memory.
82. What is a modem and why is it necessary in communications?
83. A multiplexer is commonly used in communications. Explain what it is used for and briefly describe two methods of implementation.
84. Describe a binary tree and how it may be implemented in main memory. How does it facilitate  sorting?
85. Explain the use of an accumulator in the CPU.
86. An instruction consists of two parts. What are they?
87. Explain the difference between absolute and relocatable programs.
88. Explain Simplex, Duplex and Half-Duplex transmission.
89. Describe, with the aid of an example, the use of batch and hash totals in batch processing.
90. Describe three actions carried out by the control unit.
91. Explain, using 4362 as an example, how a check digit may be used to detect a transcription error in an account number.
92. Describe three types of documentation which should accompany any software.
93. Why is it not necessary to take a backup copy of a master file after it has been processed sequentially?
94. What methods might be employed to ensure security against loss or corruption of a master file in a direct access system?
95. What methods might be employed in a multi-access system such as public administration to ensure privacy of data?
96. Briefly describe the three stages of compilation.
97. What is the purpose of the symbol table during both compilation and the assembly process?
98. State three advantages of interrupts rather than a polling system.
99. In assembly language, what is meant by a directive? Give an example.
100. In assembly language, what is a macro?
101. Describe three functions of a job scheduler in an operating system that supports multi-access and multi-programming.
102. Unlike a disk, a printer is an unshareable device. Describe a strategy for allowing it to be shared by more than one job in multiprogramming.
103. List the advantages to the customer and the management of a supermarket using bar codes and POS terminals.
104. Describe, with examples, one, two and zero address systems for machine code instructions.
105. Outline the steps needed to:

        add two floating point numbers

        multiply two floating point numbers

106. Give two examples of syntax errors in a program.
107. Explain the meaning of and give two examples of semantic errors.
108.  A program which is free of syntax and semantic errors will compile but may have other errors. Give two examples of errors which may occur.
109. How might logic errors be detected?
110. Distinguish between centralised and distributed processing.
111. Discuss the problems of representing zero in floating point representation.
112. In what type of processing system is a Job Control Language used? Give three items which a JCL may provide about a job.
113. What are the advantages and disadvantages of compilation over interpretation in the development and running of programs?
114. Explain prototyping and its advantages.
115. What is a transducer? Give an example of a use in computing.
116. Explain, with the aid of an example, an embedded system.
117. State four functions offered by electronic mail.
118. Describe a key- to-disk system.
119. Explain, with the aid of an example, data logging.
120. In a relational database, what is:

        i)        an entity

        ii)        an attribute

        iii)         a relationship ?

Give an example of each with reference to a driving school database

121. Explain, with examples :

        expert system

        artificial intelligence

122. State a type of high level language which might be suitable for each of the following applications. Give two features in each case which make it suitable:

        i)        engineering or mathematical

        ii)        expert systems or artificial intelligence

3. heating control system

123. Why was it advantageous to use C to write the Unix operating system instead of using assembly language?
124. By what main methods would you accomplish the actual changeover to a new computerised system and what are their relative merits?
125. How would the precision of arithmetic be improved in a 16-bit computer?
126. Explain automatic sequence control.
127. What is the ‘stored program concept’?
128. One of the functions of an operating system in multiprogramming is memory management. What does the operating system need to do and how might it be achieved?
129. On what basis might the schedular issue a high priority to a process in multiprogramming?
130. Why can priorities not normally be issued in a multi-access system? What scheduling policy might be used instead?
131. Why is normalisation generally carried out on a relational database? Give a simple example to illustrate your answer.
132. Discuss briefly the problems of concurrent access in databases and how it may be overcome.
133. State three provisions of the UK Data Protection Act concerning the storage of and access to personal data within computer systems. Name some exemptions from these provisions by the act.
134. What is meant by the term ASCII character?
135. State one advantage and one disadvantage of static ram over dynamic ram.
136. Explain the term bit-mapped screen display.
137. What are the advantages of packet switching?
138. Describe two checks which may be made to detect errors in data transmission
139. What is the purpose of the process descriptor (process control block) of a process in multiprogramming? Give three items of information contained in this block..
140. Give three error conditions which would give rise to an interrupt.