Computer Fundamentals Multiple Choice Questions on “The Control Unit”.
1. ____________ is the raw material used as input and __________ is the processed data obtained as output of data processing.
a) Data, Instructions
b) Instructions, Program
c) Data, Program
d) Program, Code
Answer: a
Clarification: Data can be assumed as a raw material which, in turns after processing gives the desired output in the form of instructions. Further, a set of ordered and meaningful instructions is known as a program.
2. Which of the following is not a characteristic of a computer?
a) Diligence
b) I.Q.
c) Accuracy
d) Versatility
Answer: b
Clarification: The Computer system has no I.Q. of its own. It does only what it is programmed to do. It cannot take decisions of its own.
A computer is diligent because it can work continuously for hours without getting any errors or without getting grumbled.
The accuracy of a computer is consistently high and its level of accuracy depends on its design. A computer can perform any task if, it can be broken down into a series of logical steps. Therefore, a computer is versatile.
3. A decoder is required in case of a ______________
a) Vertical Microinstruction
b) Horizontal Microinstruction
c) Multilevel Microinstruction
d) All types of microinstructions
Answer: a
Clarification: There are two types of microinstructions: Horizontal and Vertical.
In a horizontal microinstruction, each bit represents a signal to be activated whereas, in case of vertical microinstruction bits are decoded and, the decoder then produces signals.
4. The part of a processor which contains hardware necessary to perform all the operations required by a computer:
a) Data path
b) Controller
c) Registers
d) Cache
Answer: a
Clarification: A processor is a part of the computer which does all the data manipulation and decision making. A processor comprises of:
A data path which contains the hardware necessary to perform all the operations. A controller tells the data path what needs to be done.
The registers act as intermediate storage for the data.
5. What does MAR stand for?
a) Main Address Register
b) Memory Access Register
c) Main Accessible Register
d) Memory Address Register
Answer: d
Clarification: MAR is a type of register which is responsible for the fetch operation. MAR is connected to the address bus and it specifies the address for the read and write operations.
6. If the control signals are generated by combinational logic, then they are generated by a type of _______________ controlled unit.
a) Micro programmed
b) Software
c) Logic
d) Hardwired
Answer: d
Clarification: The main task of a control unit is to generate control signals. There are two main types of control units:
A hardwired control unit generates control signals by using combinational logic circuits and the Micro programmed control unit generates control signals by using some softwares.
7. Which is the simplest method of implementing hardwired control unit?
a) State Table Method
b) Delay Element Method
c) Sequence Counter Method
d) Using Circuits
Answer: a
Clarification: There are 3 ways of implementing hardwired control unit:
A state table is the simplest method in which a number of circuits are designed based on the cells in the table.
A delay element method consists of a flowchart drawn for the circuit. A D-flip flop is used as a delay element.
A sequence counter method used k-modulo counter as a replacement for k delay elements.
8. A set of microinstructions for a single machine instruction is called ___________
a) Program
b) Command
c) Micro program
d) Micro command
Answer: c
Clarification: For every micro-operation, a set of microinstructions are written which indicate the control signals to be activated. A set of microinstructions is a micro program. The address of the next microinstruction is given by a Micro-program counter.
9. Micro-program consists of a set of microinstructions which are strings of 0s and 1s.
a) True
b) False
Answer: a
Clarification: The computer understands only binary language. So, the micro-program should have instructions which are in the form of 0s and 1s. Each output line of the micro-program corresponds to one control signal.