Dixon,
In assembly:
MOV A,00H ;Moves the data in internal ram location 00H to the A register.

MOVC A,00H ;Moves the code byte located at 00H code space into the A register.

MOVX A,00H ;Moves the data in external ram (if you have it) location 00H into the A register.

In C:

unsigned char data my_variable;
unsigned char data my_other_variable;

my_variable = my_other_variable;
//Places data at my_other_variable in my_variable

unsigned char code my_constant = 0x03;

my_variable = my_constant;
//Places 0x03 (which is located in code space) into my_variable.

unsigned char xdata my_last_variable;

my_variable = my_last_variable;

//Places the contents of my_last_variable (located in external ram) into the internal ram variable my_variable.

More?
Allen