The 8086 interrupt system: IVT layout at 00000h-003FFh, the six-step hardware acknowledgment sequence, writing correct ISRs with register save/restore/EOI/IRET, vector installation via DOS INT 21h, and a complete worked timer ISR example.
How the Intel 8086 splits work between the Bus Interface Unit (BIU) and Execution Unit (EU) to create a two-stage pipeline, with the complete 40-pin signal reference (minimum and maximum mode), T-state bus cycle timing, even/odd memory banks, and the full I/O subsystem including 8255 PPI, 8259 PIC, and 8253 timer.
Complete 8086 addressing modes reference: all 9 modes with EA formulas, default segment rules, clock-cycle costs, the [BX+SI] vs [BX+DI] timing asymmetry, and all five string instructions (MOVS, CMPS, SCAS, LODS, STOS) with REP/REPE/REPNE, auto-adjustment table, and worked examples.
All 9 flags of the 8086 flag register explained: CF, PF, AF, ZF, SF, OF (status) and TF, IF, DF (control) with exact set/clear conditions, the CF vs OF unsigned/signed distinction, the four traps that catch every beginner, and a complete conditional jump reference.
The complete 8086 stack reference: SS:SP model, byte-level PUSH/POP mechanics, near and far CALL/RET, stack frame setup with BP for parameters and locals, and the INT/IRET stack protocol.
A complete 8086 assembly program implementing the Sieve of Eratosthenes to find all prime numbers up to 50. Includes annotated source code, algorithm walkthrough, how-the-code-works breakdown, sample output, and a common-mistakes table.
A fully working 8086 assembly language calculator that performs addition, subtraction, multiplication, and division on 16-bit numbers. Includes annotated source code, algorithm walkthrough, sample output, and a common-mistakes table.
A complete guide to handling the 8086 external timer interrupt INT 08h. Covers the interrupt vector table, how the CPU dispatches interrupts, saving and restoring the original BIOS handler, writing a far ISR that increments a tick counter, chains correctly, and exits safely — with a common-mistakes table.
A complete guide to 8086 assembly stack operations. Covers how the stack works (SP, SS, LIFO), what PUSH and POP do to memory, how CALL saves a return address and RET retrieves it, and a fully annotated working program that demonstrates all four instructions together.
This blog post details an 8086-assembly program that computes the power of a number using the Exponentiation by Squaring algorithm (O(log n) efficiency). While a standard iterative approach multiplies the base n times (taking O(n) time), exponentiation by squaring—also known as binary exponentiation—works by breaking the exponent down into its binary components. By squaring the base in each step and only multiplying it into the result when a bit in the exponent is set, we drastically reduce the computational load. For example, calculating x32 requires only 5 multiplications instead of 31. This example demonstrates advanced assembly concepts like bitwise manipulation, conditional branching, and efficient arithmetic optimization. Let’s get started! Logic Breakdown: The algorithm follows the mathematical identity of Binary Exponentiation: Check Exponent: If it's zero, stop. Odd Case: If the current exponent is odd, multiply the running result by the current base. Square and Halve: Regardless of odd/even, square the base and divide the exponent by 2. Loop: Continue until the exponent is exhausted. Let's visualize it's working for 53. StepBase ExponentResult ActionInitial531Start loopIter 153 (Odd)51 X 5 = 5Square251552 = 25, 3/2 = 1Iter 2251 (Odd)1255 X 25 = 125Square6250125252 = 625,1/2 = 0Exit-0125Loop terminates