COA Interview Questions
1. What are the types of computer?
Personal computer, notebook computer, workstations, enterprise or mainframes.
2. What are the functional units of a computer?
Input unit, memory unit, arithmetic and logic unit, output unit and control unit.
3. What is a program?
A list of instructions that performs a task is called a program. Usually the program is stored in memory.
4. What is object program?
Compiling a high-level language source program in to a list of machine instructions constituting a machine language program is called an object program. It is the assembled machine language program.
5. What do you mean by bits?
Each number, character, or instruction is encoded as a string of binary digits called as bits, each having one of two possible values, 0 or 1.
6. Define RAM.
Memory in which any location can be reached in a short fixed time after specifying its address is called random-access memory (RAM).
7. Define word length.
The number of bits in each word is often referred to as the word length of the computer. Typical word lengths range from 16 to 64 bits.
8. Define memory access time?
The time required to access one word is called as memory access time. This time is fixed and independent of the location of the word being accessed. It typically ranges from a few nanoseconds (ns) to about 100 ns for modern RAM units.
9. What is memory hierarchy?
The memory of a computer is normally implemented as a memory hierarchy of three or four levels of semiconductor RAM units with different speeds and sizes. The small, fast RAM units are called caches. The large and slowest unit is referred to as main memory.
10. What is primary storage and secondary storage?
Primary memory is a fast memory that operates at electronic speeds. It is expensive. Secondary memory is used when large amounts of data and many programs have to be stored, particularly for information that is accessed infrequently.
COA Interview Questions
11. What are registers?
Registers are high speed storage elements. Each register can store one word of data. Access time to registers is faster than access time to the fastest cache memory.
12. What are timing signals?
Timing signals are generated by the control circuits. These are signals that determine when a given action should take place. Data transfers between the processor and memory are also controlled by the control unit through the timing signals.
13. Explain briefly the operation of Add LOCA, R0.
This instruction adds the operand at memory location LOCA to the operand in a register in the processor, R0, and places the sum in to register R0. The original contents of location LOCA are preserved, whereas those of R0 are overwritten.
14. What is instruction register?
The instruction register (IR) holds the instruction that is currently being executed. Its output is available to the control circuits which generate the timing signals that control the various processing elements involved in executing the instruction.
15. What is program counter?
The program counter (PC) keeps track of the execution of a program. It contains the memory address of the next instruction to be fetched and executed.
16. What is MAR and MDR?
The memory address register (MAR) holds the address of the location to be accessed. The memory data register (MDR) contains the data to be written into or read out of the addressed location.
17. What is an interrupt?
An interrupt is a request from an I/O device for service by the processor. The processor provides the requested service by executing an appropriate interrupt-service routine.
18. Define bus.
A group of lines that serves as a connecting path for several devices is called a bus. In addition to the lines that carry data, the bus must have lines for address and control purposes.
19. What is a compiler?
It is a system software program that translates the high-level language program into a suitable machine language program.
20. What is a text editor?
It is a system program used for entering and editing application programs.
COA Interview Questions
21. What is a file?
A file is simply a sequence of alphanumeric characters or binary data that is stored in memory or in secondary storage. A file can be referred by a name chosen by the user.
22. Define OS.
Operating system (OS) is a large program, or a collection of routines, that is used to control the sharing of and interaction among various computer units as they execute application programs.
23. What is multiprogramming or multitasking?
The operating system manages the concurrent execution of several application programs to make the best possible use of computer resources. This pattern of concurrent execution is called multiprogramming or multitasking.
24. What is elapsed time?
It is a measure of performance of the entire computer system. It is affected by the speed of the processor, the disk and the printer.
25. What is processor time?
The sum of the periods during which the processor is active is called the processor time.
26. What are clock and clock cycles?
The timing signals that control the processor circuits are called as clocks. The clock defines regular time intervals called clock cycles.
27. Give the basic performance equation.
T = (N * S)/R
Where, T – performance parameter
N – actual number of instruction executions
S – average number of basic steps needed to execute one machine instruction
R – clock rate in cycles per second.
28. What is pipelining?
The technique of overlapping the execution of successive instruction for substantial improvement in performance is called pipelining.
29. What is superscalar execution?
In this type of execution, multiple functional units are used to create parallel paths through which different instructions can be executed in parallel. so it is possible to start the execution of several instructions in every clock cycle. This mode of operation is called superscalar execution.
30. What is RISC and CISC?
The processors with simple instructions are called as Reduced Instruction Set Computers(RISC). The processors with more complex instructions are called as Complex Instruction Set Computers (CISC).
COA Interview Questions
31. Define SPEC rating.
Running time on the reference computer
SPEC rating = Running time on the computer under test
32. Define byte addressable memory.
Byte locations have addresses 0,1,2….Thus if the word length of the machine is 32 bits, successive words are located at addresses 0,4,8….with each word consisting of 4 bytes. This is called byte addressable memory.
33. What is big-endian and little-endian?
The name big-endian is used when lower byte addresses are used for the more significant bytes (the leftmost bytes) of the word. The name little-endian is used when lower byte addresses are used for the less significant bytes (the rightmost bytes) of the word.
34. What is aligned address?
Words are said to be aligned in memory if they begin at a byte address that is a multiple of the number of bytes in a word.
35. Explain briefly the operation of ‘load’.
The load operation transfers a copy of the contents of a specific memory location to the processor. The memory contents remain unchanged. To start a load operation, the processor sends the address of the
desired location to the memory and requests that its contents be read. The memory reads the data stored at that address and sends them to the processor.
36. Explain briefly the operation of ‘store’.
The store operation transfers an item of information from the processor to a specific memory location, destroying the former contents of that location. The processor sends the address of the desired location to the memory, together with the data to be written into that memory location.
37. What is register transfer notation?
R3 <- [R1] + [R2]
This type of notation is known as register transfer instruction (RTN). The right-hand side of an RTN expression always denotes a value, and the left-hand side is the name of a location where the value is to be placed, overwriting the old contents of that location.
38. What is a one address instruction?
The instruction that contains the memory address of only one operand is called one address instruction.
Eg. Load A, Store A.
39. What is a two address instruction?
The instruction that contains the memory address of two operands is called two byte address instruction.
Eg. Add A,B , Move B,C.
40. What is a three address instruction?
The instruction that contains the memory address of three operands is called three byte address instruction.
Eg. Add A,B,C.
COA Interview Questions
41. What is a zero address instruction?
Instructions in which the locations of all operands are defined implicitly is called zero address instruction. Such instructions are found in machines that store operands in a structure called push down stack.
42. What is straight line sequencing?
To begin executing a program, the address of its first instruction must be placed into PC. Then the processor control circuits use the information in the PC to fetch and execute instructions, one at a time, in the order of increasing addresses. This is called straight line sequencing.
43. Define conditional branch.
A conditional branch instruction causes a branch only if a specified condition is satisfied. If the condition is not satisfied, the PC is incremented in the normal way and next instruction in the sequential address is
fetched and executed.
44. Define conditional code flags.
The processor keeps track of information about the results of various operations for use by subsequent conditional branch instructions. This is done by recording the required information in individual bits called as conditional code flags.
45. Define conditional code register (OR) status register.
The conditional code flags are usually grouped together in a special processor register called conditional code registers or status registers.
46. What are the four commonly used flags?
- N (negative) – set to 1 if the result is negative; otherwise, cleared to 0
- Z (zero)- set to 1 if the result is 0; otherwise, cleared to 0
- V (overflow) – set to 1 if arithmetic overflow occurs; otherwise, cleared to 0
- C (carry)- set to 1 if the carry-out results from the operation; otherwise, cleared to 0
47. What is addressing modes?
The different ways in which the location of a operand is specified in an instruction is referred to as addressing modes.
48. What are the various addressing modes?
Register mode, absolute mode, immediate mode, indirect mode, index mode, relative mode, auto increment mode, auto decrement mode.
49. Define register mode addressing.
In register mode addressing the operand is the contents of a process register. The name of the register is given in the instruction.
50. Define absolute mode addressing.
In absolute mode addressing the operand is in a memory location. The address of this location is given explicitly in the instruction. This is also called direct mode addressing.
COA Interview Questions
51. Define immediate mode addressing.
In immediate mode addressing, the operand is given explicitly in the instruction.
Eg. Move #200,R0.
52. Define indirect mode addressing.
In indirect mode addressing the effective address of the operands is the content of a register or memory location whose address appears in the instruction.
Eg: Add (R2),R0.
53. What is a pointer?
The register or memory location that contains the address of an operand is called a pointer.
Eg: A= *B. Here B is a pointer variable.
54. Define index mode addressing.
In index mode addressing, the effective address of the operand is generated by adding a constant value to the register.
EA= X + [Ri].
55. Define relative mode addressing.
In relative mode addressing the effective address is determined by the index mode using the program counter in the place of the general purpose register Ri.
56. Define Auto increment mode.
In this mode the effective address of the operand is the contents of a register specified in the instruction. After accessing the operand, the contents of this register are automatically incremented to point to the next item in a list. It can be written as (Ri)+.
57. Define Auto decrement mode.
In this mode the contents of a register specified in the instruction are first automatically decremented and then used as the effective address of the operand. . It can be written as -(Ri).
58. What are mnemonics?
When writing programs for a specific computer, words such as Move, Add, Increment and Branch are replaced by acronyms such as MOV, ADD, INC and BR. This is called mnemonics.
59. What is an assembler?
Programs written in assembly language can be automatically translated in to a sequence of machine instructions by a program called an assembler.
60. What is a source program?
The user program in its original alphanumeric text format is called a source program.
COA Interview Questions
61. What are assembler directives?
Consider the example SUM EQU 200. This statement does not denote an instruction that will be executed when the object program is run. This will not even appear in the object program. It simply informs the assembler that the name SUM should be replaced by the value 200 wherever it appears in
the program. Such statements are called assembler directives.
62. What is symbol table?
As the assembler scans through a source program, it keeps track of all names and the numeric values that correspond to them in a table called symbol table. Thus, when a name appears a second time, it is replaced with its value from the table.
63. What is a two pass assembler?
During the first pass of the assembler it creates a complete symbol table. At the end of this pass, all the names will be assigned numeric values. The assembler then goes through the source program second time and substitutes values for all names from the symbol table. Such an assembler is called a two-pass assembler.
64. What is a loader?
The assembler stores the object program on a magnetic disk. The object program must be loaded into the memory of the computer before it is executed. For this to happen, another utility program must already be loaded in the memory. This program is called a loader.
65. What is the use of debugger program?
The debugger program enables the user to stop execution of the object program at some points of interest and to examine the contents of various processor registers and memory locations.
66. What are device interface?
The buffer registers DATAIN and DATAOUT and the status flags SIN and SOUT are part of circuitry and they are commonly known as device interface.
67. Define memory mapped I/O.
Many computers use an arrangement called memory mapped I/O in which some memory address values are used to refer to peripheral device buffer registers, such as DATAIN and DATAOUT. This no special instructions are needed to access the contents of these registers.
68. What is a stack?
A stack is a list of data elements, usually words or bytes , with the accessing restriction that elements can be added or removed at one end of the list only. This end is called the top of the stack, and the other end is called the bottom of the stack.
69. Why is stack called as last-in-first-out?
Stack is called as last-in-first-out (LIFO), because the last data item placed on the stack is the first one removed when retrieval begins. The term push is used to describe placing a new item on the stack and pop is used to describe removing the top item from the stack.
70. What is a stack pointer?
Stack pointer (SP) is a processor register that is used to keep track of the address of the element of the stack that is at the top at any given time. It could be one of the general purpose registers or a register dedicated to this function.
71. What is a queue?
Queue is a data structure similar to the stack. Here new data are added at the back (high address end) and retrieved from the front (low address end) of the queue. Queue is also called as first-in-first-out (FIFO).
Important Interview Questions
- Top 100 Data Structures Interview Questions
- Top 100 DBMS Interview Questions
- Best Top 30 C Language Interview Questions
- Best Top 50 Data Structures Interview Questions
- Top 100 Operating System Interview Questions
- Top 100 Python Interview Questions
- Top 100 SQL Interview Questions
- Best Top 100 Computer Architecture | COA Interview Questions
- Top 100 Java Interview Questions
- Best Top 50 JAVA Interview Questions