ALU 101 study guide
ALU 101 · Work through your exam, one topic at a time.
ALU 101 is a foundational credential covering the arithmetic logic unit - the circuit block at the center of every processor that performs integer arithmetic and bitwise operations. It suits students in computer engineering, computer science, or digital electronics who have completed introductory logic design and want to demonstrate that they understand how data is represented, manipulated, and routed inside a CPU datapath. The ALU 101 study guide has 6 sections and about 1,949 words.
01Arithmetic Logic Unit Fundamentals
The arithmetic logic unit is the combinational circuit that performs integer arithmetic and bitwise logic on operands supplied by the datapath. Candidates should be comfortable with the ALU's role as a function unit : a set of operations selected by control lines, with result and status outputs.
367 words, about 2 min02Number Systems and Data Representation
You must convert fluently among binary, octal, hexadecimal, and decimal, and perform signed representations: sign-magnitude, one's complement, and two's complement. Two's complement dominates because it gives a single representation of zero and lets addition work without sign logic.
299 words, about 1 min03Boolean Algebra and Logic Gates
Candidates must know the standard Boolean identities: commutative, associative, distributive, identity (A+0=A, A·1=A), null (A+1=1, A·0=0), idempotent (A+A=A), complement (A+A'=1, A·A'=0), absorption (A+AB=A), and De Morgan's laws: (A+B)' = A'·B' and (A·B)' = A'+B'. Be able to simplify expressions and convert between sum-of-products (SOP) and product-of-sums (POS) forms, and to read a truth table into a canonical expression.
311 words, about 2 min04Combinational and Sequential Logic
Combinational logic has no memory: outputs depend only on current inputs (adders, multiplexers, decoders, comparators). Sequential logic stores state: outputs depend on inputs and prior state, clocked by a clock signal (flip-flops, registers, counters).
332 words, about 2 min05ALU Operations and Instruction-Level Behavior
Understand how assembly instructions drive the ALU: ADD, SUB, AND, OR, XOR, NOT, shifts, compares, and increments. Know that a compare is usually a subtraction whose result is discarded but whose flags are kept.
326 words, about 2 min06Datapath, Registers, and Control
The datapath is the network of registers, the ALU, multiplexers, and buses that move and transform data. Candidates should be able to describe a simple processor datapath: program counter, instruction register, register file, ALU, and memory interface.
314 words, about 2 min