How to reduce the length of compiled code in keil C51 language programming

1. The C51 program for multiplication and division of integers is relatively large, about 9 bytes, so try not to do multiplication and division.

For example: uchar a=6; a=a*6; the second line of code requires 9 bytes, while the usual statement only has 2B.

2. Statements that define variables but do not assign values ​​or participate in calculations are not considered code. Use short variables if possible to save RAM and code space.

For example: uchar a; This sentence has no code length. But if you assign a non-zero value uchar a=5; to character type, the code length will be 3B.

uint a=5; the integer variable assignment requires 6B bytes, which is relatively large, so define a short variable if possible.

unsigned long int a=6.0; or long int a=6.0; will add 9 bytes of code. The same is true for assigning integers and floating-point numbers.

3. For long integer variables, the compiled code is longer when signed variables participate in self-addition operations than unsigned variables, so try to use unsigned floating-point numbers.

For example: long a=2; a++; or unsinged long int a=2; a++; The code should be 15 bytes shorter. a--shortened by 12 bytes

If we replace self-increment with addition assignment, the code length is the same. a+=2; there is no difference between the two definitions.

4. Do not perform multiplication and division operations on floating point numbers. The code length will be too large. The code will be several hundred bytes longer. It is not worth it. It is better to use other methods instead.

5. For similar operations, they should be written together. For example, if you call a subroutine in the middle and then come back to calculate data, the code will be much longer. (How can the number of in and out operations not be large?)

6. When defining a variable, assign a value, and then assign the value again in the next line, which will shorten the code. For example: uint a=2; a=2; Having an extra line actually shortens the code.

For example: uint a=3, b=3; a=b; Although it is redundant, the consumption of the previous code is offset. It is equivalent to not adding any code