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3. Digital Logic from Zero

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Start with Volume 00. It explains what digital logic is, why computers use only two values and how the course works. It ends with your first circuit: one light controlled by two switches. Then take the volumes in order - each one uses only what came before it.

This course assumes nothing. You do not need to know any electronics or any programming. If you can count and follow a table, you can start.

Every truth table, circuit diagram and timing diagram here was checked by a simulator before it was published, so a table always matches its circuit. Each new word is underlined with dots - point at it (or tap it) to see what it means. Every sub-module ends with a quick check, so you know whether an idea has landed before you move on.

Full syllabus

Part I - Numbers and gates

• 00 Start Here: What Digital Logic Is What digital logic is, why computers use only two values, how this course works, and a first circuit: one light controlled by two switches. Live
• 01 The Numbers Computers Use Binary, hexadecimal and octal, converting between bases, negative numbers in two's complement, and the codes computers use: BCD, Gray code and ASCII. Live
• 02 Logic Gates The seven basic gates, truth tables and timing diagrams, why NAND and NOR can build anything, and what gates look like on real chips. Live

Part II - Simplifying logic

• 03 Boolean Algebra The rules of Boolean algebra, De Morgan's theorems, sum-of-products and product-of-sums forms, minterms and maxterms, and simplifying a circuit step by step. Live
• 04 K-Maps and Simplification Karnaugh maps for two, three and four variables, don't-care conditions, product of sums from a map, and hazards - the glitches a correct circuit can make. Live

Part III - Building blocks

• 05 Combinational Building Blocks Multiplexers, decoders and demultiplexers, encoders and priority encoders, comparators and seven-segment display decoders - and building any function from a multiplexer or a decoder. Live
• 06 Arithmetic Circuits Half and full adders, the ripple-carry adder, subtraction with two's complement, overflow, and the faster carry look-ahead adder. Live

Part IV - Memory and time

• 07 Latches and Flip-Flops Why circuits need memory, the SR latch, the D latch, the D flip-flop, JK and T flip-flops, and setup time, hold time and clock-to-Q delay. Live
• 08 Registers, Counters and Shift Registers Registers, shift registers, ring and Johnson counters, ripple and synchronous counters, and designing a counter for any sequence. Live

Part V - Real chips and revision

• 09 Memory, ADC/DAC and Logic Families ROM and RAM, programmable logic, digital-to-analogue and analogue-to-digital converters, and the TTL and CMOS logic families. Live
• 10 Digital Logic Problem Vault A formula and fact sheet, GATE-style practice problems written for this course with full solutions, and interview and viva questions. Live

What you need before starting