Explain RAM and ROM with a block diagram.

RAM or Random Access Memory is the central storage unit in a computer system. It is the place in a computer where the operating system, application programs and the data in current use are kept temporarily so that they can be accessed by the computer `s processor. The more RAM a computer has, the more data a computer can manipulate. It is also called the Read/ Write memory and is the temporary memory of a computer. It is said to be Volatile since its contents are accessible only as long as the computer is on. The contents of RAM are cleared once the computer is turned off.

Step to be followed to transfer a new word to be stored into memory are:

1. The binary address of the desired word is applied into the address lines.
2. The data bits that must be stored in memory are applied into the data input lines.

Read Only Memories (ROM)

ROM or Read only Memory is a special type of memory which can only be read and contents of which are not lost even when the computer is switched off. It typically contains manufactures instructions. Among other things, ROM also stores an initial program called the bootstrap loader whose function is to start the computer software operating, once the power is turned on. ROM can be manufacture-programmed or user-programmed.

• While manufacturer-programmed ROMs have data burnt into the circuitry, user programmed ROMs can have the user load and then store read-only programs.
• PROM or programmable ROM is the name given to such ROMs.

ROM dose not need a read control line since at any time, the output lines automatically provide the n hits of the word selected by the address value. ROM is internally constructed with decoders and a set of OR gates. a ROM generates an input output relating specified by truth table. It is considered as a combinational circuit.

Applications of ROM

1. ROM is widely used in the design of digital systems.
2. It is also employed in the design of control units for digital computers. They are used to store coded information that represents the sequence of internal control variables needed for enabling the various operations in the computer. The control unit is then called micro- programmed control unit.
3. It is used as a memory unit, to store fixed programs that are not to be altered and for tables of constants that are not subject to change.

Originally published at https://cselearnmore.com on March 18, 2021.