Most (99%+) of microprocessors available to the consumer and/or embedded market are either Big Endian or Little Endian; this almost never actually matters. However, sometimes one needs to write endian specific code. Here's how to have code identify if it's running on a big endian or little endian machine:
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No C programmer can call himself (or herself) a real programmer without having seen (and been amazed by) Duff's Device. It was invented as a more efficient alternative to regular loop unrolling used in copying bytes from memory to a register (each byte went to the same address in memory), by handling the case when there are "leftover" bytes after a full unroll.
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Quiz:
What does the following code print:
int i,j;
float k;
i = 5;
j = 2;
k = i/j;
printf("%f\n",k);Sometimes, you'll have a scenario with two variables, and you need to use one of them based on a simple test. Rather than a long and awkward if / else statement, C allows the use of the ? : form. It is perfectly acceptable to write:
int i,j,k,l;
...
i = (j > 5? k : l)which will set i to k if j is greater than 5, and l otherwise.
Another common use is [sf]?printf statements:
printf("The test %s\n",(status == OK) ? "passed" : "failed");However, one can't use it to handle selective assignments. The following code is illegal:
int i,j,k;
...
((i>5) ? j : k) = 5;This cannot be used to choose whether j or k is set to 5.
There is, however a way this can be done. Using pointer, we can select which one to deference:
*((i>5) ? &j : &k) = 5;This will work.
