I'm not completely on board with #4 (initialization of variables). I agree that 'declaring and then assigning a value' _within the same block_ vs 'initialized d

I'm not completely on board with #4 (initialization of variables). I agree that 'declaring and then assigning a value' _within the same block_ vs 'initialized declaration' has no speed gains, only downsides. However, if the assignment can happen in a _different block_ (maybe inside an 'if' block) you could save 1 memory write, depending on how many times the if condition is satisfied. This obviously optimizes for speed at the expense of maintainability, and it's for the programmer to make intelligent trade offs, but the fact is that one method is faster than the other. Silly example that decrements 'a' repeatedly if condition is non-zero: //temp = 0 inside if block int dec(int a, int condition) { int temp; if (condition) { temp = 0; //<-- memory write depends on condition //compute something here in a loop while (temp < a) { a -= (temp++); } } return a; } //temp = 0 at declaration int dec2(int a, int condition) { int temp = 0; // <-- memory write always executed if (condition) { //compute something here in a loop while (temp < a) { a -= (temp++); } } return a; } We can disassemble the output to verify that dec() will only write to memory if the condition was satisfied (see 400458), while dec2() will always write into temp (see 400482): # <dec> 400448: push %rbp 400449: mov %rsp,%rbp 40044c: mov %edi,0xffec(%rbp) 40044f: mov %esi,0xffe8(%rbp) 400452: cmpl $0x0,0xffe8(%rbp) # if (condition) 400456: je 400473 <dec+0x2b> 400458: movl $0x0,0xfffc(%rbp) # temp = 0 <-- depends on condition 40045f: jmp 40046b <dec+0x23> # while 400461: mov 0xfffc(%rbp),%eax 400464: sub %eax,0xffec(%rbp) 400467: addl $0x1,0xfffc(%rbp) 40046b: mov 0xfffc(%rbp),%eax 40046e: cmp 0xffec(%rbp),%eax 400471: jl 400461 <dec+0x19> # loop 400473: mov 0xffec(%rbp),%eax # return a 400476: leaveq 400477: retq # <dec2> 400478: push %rbp 400479: mov %rsp,%rbp 40047c: mov %edi,0xffec(%rbp) 40047f: mov %esi,0xffe8(%rbp) 400482: movl $0x0,0xfffc(%rbp) # temp = 0 <-- always executed 400489: cmpl $0x0,0xffe8(%rbp) # if (condition) 40048d: je 4004a3 <dec2+0x2b> 40048f: jmp 40049b <dec2+0x23> # while 400491: mov 0xfffc(%rbp),%eax 400494: sub %eax,0xffec(%rbp) 400497: addl $0x1,0xfffc(%rbp) 40049b: mov 0xfffc(%rbp),%eax 40049e: cmp 0xffec(%rbp),%eax 4004a1: jl 400491 <dec2+0x19> # loop 4004a3: mov 0xffec(%rbp),%eax # return a 4004a6: leaveq 4004a7: retq The above code was compiled with gcc 4.1.2 on amd64/linux. gcc -O2 and gcc -O3 completely do away with the 'temp' variable and generate fewer instructions.