6.1.7 Expressions and Operators

Expressions can consist of unary operators (one operand, e.g., not) or binary operators (two operands, e.g., +). The operators allowable in expressions are listed in the table below.

Operators within expressions are evaluated left to right, thus the expression 5 + 1 * 2 will yield the value 12. Use parenthesis to change the order of operator execution, for example 5 + (1 * 2) will yield the value 7.

With the exception of the equality (e.g. =) and relational operators (e.g. >=), all the operators listed can be freely combined in both constant and relocatable expressions. Relocatable expressions will be evaluated by the linker at link time, after psects have been positioned and symbol values have been determined.

Table 6-5. Assembly Operators
Operator Purpose Example
* multiplication movlw 4*33,w
+ addition bra $+1
- subtraction DB 5-2
/ division movlw 100/4
= or eq equality IF inp eq 66
> or gt signed greater than IF inp > 40
>= or ge signed greater than or equal to IF inp ge 66
< or lt signed less than IF inp < 40
<= or le signed less than or equal to IF inp le 66
<> or ne signed not equal to IF inp <> 40
low low byte of operand movlw low(inp)
high high byte of operand movlw high(1008h)
highword high 16 bits of operand DW highword(inp)
mod modulus movlw 77mod4
& or and bitwise AND clrf inp&0ffh
^ bitwise XOR (exclusive or) movf inp^80,w
| bitwise OR movf inp|1,w
not bitwise complement movlw not 055h,w
<< or shl shift left DB inp>>8
>> or shr shift right movlw inp shr 2,w
rol rotate left DB inp rol 1
ror rotate right DB inp ror 1
float24 24-bit version of real operand DW float24(3.3)
nul tests if macro argument is null