Conventional Memory

What is Conventional Memory?

Conventional memory refers to the first 640 KB of the IBM compatible memory. Ideally, this is the only section of the memory that can be accessed by the operating system without needing the help of the memory manager.

Technically, this is the contiguous memory that lies before the Upper Memory Area and can be used by applications directly.

Understanding Conventional Memory

What is Conventional Memory

In a computer, the conventional memory is the initial 640 KB space of the memory and is followed by 384 KB, which is called the Upper Memory Area (UMA).

This specific section of the memory in a DOS system is available to all regular DOS programs.

The contiguous section of the conventional memory and UMA together make 1 MB of memory space, and anything beyond this amount is called either the extended memory or the expanded memory.

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This memory area is different from the upper memory blocks because these are not connected to the conventional memory and therefore cannot be used directly by the applications.

Some of the most common Some very common Disk Operating System drivers and Terminate-And-Stay-Resident Programs or TSRs that use the conventional memory are:

Conventional Memory Vs Extended Memory

How is the Upper Memory Area Significant to Conventional Memory?

The use of the Upper Memory Area helps in freeing the conventional memory by moving the device drivers and the TSRs into the upper 384 KB of a 1 MB address space. However, it leaves the 640 KB of addressable memory intact.

What is the Size of Conventional Memory

Usually, the conventional memory in DOS memory management measures the initial 640 KB of the memory space.


The conventional memory is the initial section of read-write memory that can be accessed by the application programs and the operating systems.

This specific section of the memory is mostly used by the DOS drivers and TSRs in addition to the regular DOS software for the sake of their optimization.