Terminology Used in Microprocessor and Microcontroller

Microprocessor is a single chip CPU of microcomputer. Let’s have a look at terminology used in microprocessor and microcontroller systems.

Hardware, Software and Firmware

Hardware, software, and firmware are three important components of a computer system that work together to perform various tasks.


    • Hardware refers to the physical components of a computer system, such as the central processing unit (CPU), memory, hard disk drive, motherboard, input/output devices, and peripherals.
    • These components are tangible and can be seen, touched, and manipulated.


    • Software refers to the programs and instructions that tell the computer hardware what to do.
    • Software can be divided into two categories: system software and application software.
    • System software includes the operating system, device drivers, and other utility programs that manage the computer hardware and provide a platform for running applications.
    • Application software includes programs such as word processors, web browsers, games, and multimedia players.


    • Firmware is a type of software that is embedded in hardware components and provides low-level control over the hardware.
    • It is a special type of software that is designed to perform specific tasks and is usually stored in read-only memory (ROM) or flash memory.
    • Firmware is responsible for managing the hardware and providing a communication interface between the hardware and software components.
    • Examples of firmware include BIOS firmware that controls the startup process of a computer, firmware in routers and switches, and firmware in smart home devices such as thermostats and security cameras.

Bus or System Bus

The group of wire which carries binary information from one part of system to another part is known as bus.

In computer architecture, a bus refers to a communication system that allows different components of a computer to transfer data and instructions. There are three main types of buses: the data bus, address bus, and control bus.

Data Bus:

  • The data bus is responsible for carrying data between the CPU and memory or input/output devices. It is a bi-directional bus, which means that data can be transferred in both directions.
  • The width of the data bus determines the amount of data that can be transferred at once. For example, a 32-bit data bus can transfer 32 bits (4 bytes) of data at once.

Address Bus:

  • The address bus is responsible for carrying memory addresses between the CPU and memory. It is a unidirectional bus, which means that data can only be transferred in one direction (from the CPU to memory).
  • The width of the address bus determines the maximum amount of memory that can be addressed. For example, a 32-bit address bus can address up to 2^32 bytes of memory, which is approximately 4 GB.

Control Bus:

  • The control bus is responsible for carrying control signals between the CPU and other components.
  • It is used to signal when data is ready to be transferred, when a device is ready to receive data, and when data has been successfully transferred.
  • The control bus is typically a set of unidirectional signals that are used to coordinate the actions of the different components of a computer system.

Program Memory

  • Program memory is a type of memory used in computers and other digital devices to store the executable code of a program. Also known as ROM (Read-Only Memory), it is a type of non-volatile memory that retains its contents even when the power is turned off.
  • Program memory contains the instructions that tell the CPU how to execute the program. These instructions are usually written in machine language or assembly language, which are low-level programming languages that can be executed directly by the CPU.
  • Program memory is different from other types of memory, such as RAM (Random Access Memory), because it cannot be modified once the program is written and stored in it. 
  • It is called read-only memory because it can only be read and not written to, at least not in the same way as RAM. The contents of program memory are typically set by the manufacturer of the device, or by a programmer during the development of the program.
  • Program memory is commonly used in embedded systems, such as microcontrollers, where the program is stored in ROM and executed directly from the memory. 
  • It is also used in other devices where the program needs to be stored permanently, such as in BIOS firmware in computers.

Data Memory

  • Data memory is a type of memory used in computers and other digital devices to store data temporarily during program execution. It is also known as RAM (Random Access Memory), which is a type of volatile memory that can be read from and written to.
  • Data memory is used to store variables, arrays, and other data structures that are used by a program during its execution. 
  • Unlike program memory (ROM), data memory can be written to and read from multiple times, and its contents can be modified by the program at run-time.
  • Data memory is organized into memory locations, each of which is identified by a unique address. The size of each memory location depends on the architecture of the computer system, and it is usually measured in bytes. 
  • The total amount of data memory available in a system is also determined by the architecture, and it can range from a few kilobytes in small embedded systems to several gigabytes in modern desktop computers.
  • There are several types of data memory, including static RAM (SRAM), dynamic RAM (DRAM), and synchronous dynamic RAM (SDRAM). 
  • Each type of memory has its own unique characteristics in terms of speed, cost, power consumption, and performance, and the choice of memory type depends on the specific requirements of the system.
  • Data memory is an essential component of a computer system, and its efficient use is critical for the performance and reliability of the system.

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