with Micro-C 51 do this
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/* demo1.c */
#include mc8051io.h

main()
{
unsigned char data;
serinit(9600);
data=peek(0x000);
printf("DATA mem at 0x0000 = %d", data);
data++;
poke(0x0000,data);
data = 0;
data = peek(0x0000);
printf("Data mem at 0x00 = %d", data);
while(1);
}

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. . . . compile with
cc51 demo1.c -io m=t
... you must change something ... but I think you can do :) good luck