SHL ??

SHL? Do you mean Shift-Bit Left? If so, there is no function; it is a C operator that is implemented using the RLC assembler instruction. The 8051 has no shift instruction. To shift:

unsigned char var   = 0x01;
unsigned int bigVar = 0x8000;

char   <<= 1; // shift var left by one.
bigVar >>= 4; // shift bigVar right by 4.

SHL? Do you mean Shift-Bit Left? If so, there is no function; it is a C operator that is implemented using the RLC assembler instruction. The 8051 has no shift instruction. To shift:

unsigned char var   = 0x01;
unsigned int bigVar = 0x8000;

char   <<= 1; // shift var left by one.
bigVar >>= 4; // shift bigVar right by 4.