Compare signed sensor readings
Before you start this master track
Binary and hexadecimal numbers, memory addresses, register widths, and signed arithmetic.
Master is the entry-background tier for this track. These three introductory x86-64 exercises cover registers, masks, shifts, and flags; completing them does not establish mastery of Assembly.
Guided code reading and debugging. Runnable coding challenges are available in JavaScript, Python, and SQL.
Understand it, then try it.
CMP sets processor flags as though it subtracted the second operand from the first, but leaves both operands unchanged. SETL uses those flags for a signed less-than test and writes one or zero to a byte. MOVZX then widens that byte into a clean 32-bit value by filling higher bits with zeroes.
mov eax, -4mov ebx, 2cmp eax, ebxsetl clmovzx ecx, clnopx86-64 instruction snippets in Intel/NASM syntax, not complete OS programs. Step from the first instruction through the last in a debugger, then inspect the named registers. eax, ebx, and ecx are 32-bit registers; cl is the low byte of ecx. No console output or system calls are used.
Track the values line by line. Predict the result before running this example in your own editor.