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The data memory type may be used to declare variables only. You may not declare data functions. This memory is directly accessed using 8-bit addresses and is the on-chip RAM of the 8051. It has the shortest (fastest) access time but the amount of data is limited in size (to 128 bytes or less).

Variables declared data are located in the DATA memory class.

Declare data variables as follows:

unsigned char data fast_variable;
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