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Types of Instruction Sets

Let us study instruction sets, what is an instruction set in computers, types of instruction sets, stacks, accumulators, and general-purpose registers.

A group of commands used in a machine language for CPU is an instruction set. A set of instructions or a subset of instructions that are used for the CPU and are responsible for enhancing all the performances of the CPU in any particular situation can also define the term ‘instruction set’. They are a set of codes generally in 0s and 1s as they are part of machine language. Stacks, accumulators, and general-purpose registers are types of instructions.

Instruction set 

A set of codes that can only be understood by a processor of the computer or CPU is known as an instruction set. These codes and machine languages are generally present as 1s and 0s. The movements of bits and bytes are controlled by these instruction sets present in the processor. Some common examples of instruction sets are:

  1. JUMP – jump instruction set is used to jump to any designated address of RAM.

  2. ADD – add instruction set is used to add any two numbers together. 

  3. LOAD – load instruction set is used to load any required information from the RAM to the CPU. 

Types of instruction set 

Many popular and useful instruction sets are important and useful in computer science. These sets of instructions have their advantages as well as usages. Here are the types of instruction sets:

1. Reduced instruction set computer (RISC)

RISC has only a few cycles per instruction. It has a simpler form than a complex set of instructions. RISC is also used in many supercomputers. For example, it uses a summit, which is a supercomputer. It was the world’s fastest supercomputer as per data in 2018. 

2. Minimal instruction set computers (MISC)

A few codes and a set of instructions are basic for any processor. They also include sub-codes. As a result, they are smaller and faster. A disadvantage of MISC is that it has more sequential dependencies. 

3. Complex instruction set computer (CISC)

CISC is a set of instructions with a few instructions per program. A CISC has fewer instructions than RISC. 

4. Explicitly parallel instruction computing (EPIC)

This is an instruction set that permits microprocessors that help to execute instructions in parallel software. EPIC intends to give a simpler performance. 

5. Very long instruction word (VLIW)

VLIW exploits parallelism at the instruction level. By this set of instructions, instructions are processed in sequence only in the CPU. This set of instructions improves the performance of the CPU. 

6. Zero instruction set computer (ZISC)

The instructions that do not include microinstructions are known as ZISC. They are based on the pattern matching and can be compared to networks of synapses and neurons. 

7. One instruction set computer (OISC)

The OISC set of instructions uses only one instruction for a machine language. This set of instructions is used to teach computer architecture and to compute structural computing research. 


A stack is a device used to store a set of instructions or information such that the item stored at last is the first item to pick. A stack is a memory unit in digital computers responsible for counting only. There are two types of stacks. These two types are register stack and memory stack. 

Register stacks are built using registers. A memory stack forms a logical part of the memory kept under the stack. Stacks are used to evaluate as well as backtrack algorithms. 

An advantage of stacks is that they are short and simpler instructions used to evaluate. However, they can not be accessed randomly. It is hard to access them, resulting in difficulty generating their code. 


A kind of register included in any CPU is known as an accumulator. It serves as a location for temporary storage for intermediate values. These intermediate values are a part of calculations done in mathematical and logical calculations. The set of instructions is short in accumulators. It is just temporary storage, which makes traffic memory high for its approach. 

General-purpose register 

General-purpose registers are used as temporary data storage. They are stored temporarily in microprocessors. They are used to store 8-bit data and are represented by six figures. These figures are B, C, D, H, and L. They can also form 16-bit operations. This can be done by combining the pairs of general pair registers such as HL, DE, and BC. They are short instructions. A disadvantage of the general-purpose register is that all its operands should be named. This results in a longer set of instructions. They are easy to use with computer processors. 


An instruction set holds all the commands and codes. These instructions are understood by a CPU as they control the CPU. When any instruction set is designed, the requirements of the processor are prioritised. Similarly, stack, accumulations, and GPR are also types of simpler instructions.

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Frequently asked questions

Get answers to the most common queries related to the NTA Examination Preparation.

What are six different types of general-purpose registers?

Ans. Six different general-purpose registers are B, C, D, E, H, and L. These registers can also be combined. ...Read full

What do you mean by a stack?

Ans. A stack is either a collection of data or a collection of elements. It acts as temporary storage for data. The ...Read full

What is an instruction set?

Ans. An instruction set is a set or group of commands in a machine language for the CPU. Computer processors can und...Read full

What is the function of the instruction set?

Ans. The function of an instruction set is that it is used to list all the codes and instructions for a processor. T...Read full