Ch : 1 - Computer Memory

· What is computer?

o A computer is an electronic device that manipulates information, or data. It has the ability to store, retrieve, and process data. You may already know that you can use a computer to type documents, send email, play games, and browse the Web.

o Its Data Processing unit/device

§ Data : Data is defined as facts or figures, or information that's stored in or used by a computer. An example of data is information collected for a research paper. An example of data is an email.

§ Processing : Processing is an act of changing the given data into a more useful form by applying a sequence of operations.

§ Output : Output is the final result which is obtained after the processing of data.

· Units of Measurement

o Data stored in computer :

§ A computer works on the concept of ON and OFF. The computer can only be in two states ON, i.e. 1 and OFF, i.e., 0. Based only on two numbers, i.e. 0 and 1 in different sequences, the computer stores data. A computer’s memory is measured either in Bits or Bytes. These are the basic units used to measure the computer’s memory.

o Computer memory is measured in bytes.

o A computer stores data in the form of ‘1’s’ and ‘0’s’.

o A group of 8 bits is called a byte. It can store one character.

o 1 byte = 8 bits

o The storage capacity of data storage devices is measured in Gigabytes or even Terabytes.

§ 1 Kilobyte (KB) = 1024 bytes

§ 1 Megabyte (MB) = 1024 KB

§ 1 Gigabyte (GB) = 1024 MB

§ 1 Terabyte (TB) = 1024 GB

Types of Computer Memory

o RAM : Random Access Memory - temporary memory

o ROM : Read Only Memory - permanent memory.

o Hard Disk : The hard disk can store a huge amount of data.

o CD : Compact Disc

o DVD : Digital Versatile Disc

o Blu-ray Disc : A single layer Blu-ray disc can store up to 25 GB. A double layer Blu-ray disc can store 50 GB high definition data.

o Pen Drive : Storage capacity ranging from 8 MB to 2 TB.

o Memory card : Storage capacities ranging up to 1 TB.

· Video link :

· https://youtu.be/FLQBAe0gkRA

· https://youtu.be/t3sxTKF66M0

Class 2 :

· What is Primary Memory? - Definition

o Primary memory is also known as main memory or may also refer to "Internal memory." and primary storage. All those types of computer memories that are directly accessed by the processor using data bus are called primary memory. That allows a processor to access stores running programs and currently processed data that stored in a memory location.

The use of memories is therefore mandatory in all systems using a microprocessor, including computers. An example of Primary memory is RAM and ROM that store programs. These memories are limited in capacity and manufactured by using integrated circuits (IC) or semiconductor device. Its speed of Data accessing is faster than secondary memory. It is more
expensive than secondary memory.

When you turn on the computer, Generally CPU searches for essential codes in RAM to get it. Otherwise, it goes to ROM. Yes, they both chips collectively called primary memory in a computer system

Types of Primary Memory

· RAM (Random Access Memory)

o The Word “RAM” stands for “random access memory” or may also refer to short-term memory. It’s called “random” because you can read store data randomly at any time and from any physical location. It is a temporal storage memory. RAM is volatile that only retains all the data as long as the computer powered. It is the fastest type of memory. RAM stores the currently processed data from the CPU and sends them to the graphics unit.

· ROM (Read Only Memory)

o ROM is the long-term internal memory. ROM is “Non-Volatile Memory” that retains data without the flow of electricity. ROM is an essential chip with permanently written data or programs. It is similar to the RAM that is accessed by the CPU. ROM comes with pre-written by the computer manufacturer to hold the instructions for booting-up the computer.

RAM & ROM

RAM is Random Access Memory.
ROM is Read Only Memory.

RAM is the memory available for the operating system, programs and processes to use when the computer is running.
ROM is the memory that comes with your computer that is pre-written to hold the instructions for booting-up the computer.

RAM requires a flow of electricity to retain data (e.g. the computer powered on).
ROM will retain data without the flow of electricity (e.g. when computer is powered off).

RAM is a type of volatile memory. Data in RAM is not permanently written. When you power off your computer the data stored in RAM is deleted.
ROM is a type of non- volatile memory. Data in ROM is permanently written and is not erased when you power off your computer.

There are different types of RAM, including DRAM (Dynamic Random Access Memory) and SRAM (Static Random Access Memory).
There are different types of ROM, including PROM (programmable read-only memory) that is manufactured as blank memory (e.g. a CD-ROM) and EPROM (erasable programmable read-only memory).

There are many differences between RAM and ROM memory but there are also a couple similarities (and these are very easy to remember). Both types of memory used by a computer, and they are both required for your computer to operate properly and efficiently.

o How RAM and ROM work in computer? (just for your knowledge0

o RAM is the memory available for the operating system, programs and processes to use when the computer is running. ROM is the memory that comes with your computer that is pre-written to hold the instructions for booting-up the computer. RAM requires a flow of electricity to retain data (e.g. the computer powered on).

o Video links:

Computer Home work Textbook :

Introduction of Secondary Memory

Primary memory has limited storage capacity and is volatile. Secondary memory overcome this limitation by providing permanent storage of data and in bulk quantity. Secondary memory is also termed as external memory and refers to the various storage media on which a computer can store data and programs. The Secondary storage media can be fixed or removable. Fixed Storage media is an internal storage medium like hard disk that is fixed inside the computer. Storage medium that are portable and can be taken outside the computer are termed as removable storage media

Classification of Secondary Memory

1) Hard Disk:

It is a rigid magnetic disc that is used to store data. It permanently stores data and is located within a drive unit.

It is permanently installed inside a computer.

It consists of many circular metallic plates (disks) layered with a magnetic coating.

The hard disk can store a huge amount of data.

Types of Hard Disk

1 Internal Hard Disk

2 External Hard Disk

2) CD (Compact Disc) :

It is a small plastic disc that stores and retrieves data using light.

Types of CD: