What is the size of float and double in C and C++? [duplicate]

Excerpt from the C99 standard, normative annex F (The C++-standard does not explicitly mention this annex, though it includes all affected functions without change per reference. Also, the types have to match for compatibility.): IEC 60559 floating-point arithmetic F.1 Introduction 1 This annex specifies C language support for the IEC 60559 floating-point standard. The IEC … Read more

LEA or ADD instruction?

One significant difference between LEA and ADD on x86 CPUs is the execution unit which actually performs the instruction. Modern x86 CPUs are superscalar and have multiple execution units that operate in parallel, with the pipeline feeding them somewhat like round-robin (bar stalls). Thing is, LEA is processed by (one of) the unit(s) dealing with … Read more

Difference between JE/JNE and JZ/JNZ

JE and JZ are just different names for exactly the same thing: a conditional jump when ZF (the “zero” flag) is equal to 1. (Similarly, JNE and JNZ are just different names for a conditional jump when ZF is equal to 0.) You could use them interchangeably, but you should use them depending on what … Read more