Stored-program computer¶
A computer design in which a processor fetches instructions from an internal program store, with code and data held in shared or separate memory.
Core Idea¶
A stored-program computer keeps encoded instructions in an internal program store and has a processor fetch them during execution. The instruction values select operations without rewiring the processor's control for each task. Where the store can be replaced, changing the stored instructions changes the task. The store need not be writable by the running application.[ref-7e171689d912][ref-cb35a6fb71b2]
Scope of Application¶
The test applies to computer hardware that executes instructions fetched from its own program memory. The Manchester Baby used a writable CRT store shared by instructions and numbers. The ATmega328P microcontroller fetches from Flash program memory while data occupy separate memory. Both are literal instances despite their different media and layouts.[ref-7e171689d912][ref-cb35a6fb71b2]
Clarity¶
Ask where instructions are encoded, how the processor fetches them, and how a new task can be loaded. The first two establish the identity. The third describes a particular machine's update route; it does not imply self-modifying code, a bootloader, or a common code/data memory in every case.[ref-7e171689d912][ref-cb35a6fb71b2]
Manages Complexity¶
The design separates the changing sequence of operations from the processor circuitry that fetches and executes them. The arrangement says little by itself about loading speed, protection settings, or memory-bus performance. Those must be checked for a particular machine.[ref-7e171689d912][ref-cb35a6fb71b2]
Abstract Reasoning¶
Hold the processor fixed and change the stored instruction sequence. If it executes different operations because it fetches different values, the store controls the computation. If changing tasks instead requires changing physical control wiring, stored-program execution has not been shown. Program storage is a separate question from whether code and data share memory.[ref-7e171689d912][ref-cb35a6fb71b2]
Knowledge Transfer¶
The encoded-instruction, program-store, and processor-fetch roles transfer between CRT-memory research hardware and Flash-based embedded hardware. Their loading paths and data-memory arrangements do not. The catalog's Representation Prime describes the code-to-operation relation inside both machines; instruction storage and fetch keep this entry within computer architecture.
Example¶
The Manchester Baby stored encoded operations and numbers in CRT random-access memory and read its instructions successively. A different program could be entered through a keyboard without changing circuitry. The ATmega328P instead prefetches instructions from on-chip Flash and keeps data in a separate space; a configured bootloader can update code. The contrast shows that common code/data memory and in-system rewrite are variants, while stored-instruction fetch is shared.[ref-7e171689d912][ref-cb35a6fb71b2]
Relationships to Other Abstractions¶
Current abstraction Stored-program computer Domain-specific
Parents (1) — more general patterns this builds on
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Stored-program computer is part of Representation Prime
A stored-program computer requires encoded instructions whose values represent operations and operands under a processor decoding convention.
Hierarchy path (1) — routes to 1 parentless root
- Stored-program computer → Representation → Abstraction
Neighborhood in Abstraction Space¶
Stored-program computer sits in a sparse region of the domain-specific corpus (95th percentile for distinctiveness): few abstractions share its structure, so a faithful description tends to retrieve it precisely.
Family — Unclustered & Miscellaneous (2721 abstractions)
Nearest neighbors
- Instruction Set Architecture — 0.78
- Processor Design — 0.78
- Typed assembly language — 0.78
- Register–memory architecture — 0.77
- Random-Access Machine — 0.77
Computed from structural-signature embeddings · 2026-10-17
Not to Be Confused With¶
Programmable is broader: a machine can accept a program through another control arrangement.[^ref-7e171689d912] Von Neumann shared memory is narrower: the ATmega328P has separate program and data spaces.[^ref-cb35a6fb71b2] Instruction Set Architecture specifies programmer-visible operation semantics, while a stored-program computer describes where running instructions reside and how they reach the processor.
References¶
[^ref-7e171689d912]: University of Manchester Computer50 archive, “The Manchester Small Scale Experimental Machine — The Baby”, Background paragraphs on CRT store, stored instructions, successive reads, and keyboard program replacement; Specification on store and input. University-hosted historical account, directly inspected; cited for this machine's described design, not a disputed universal priority claim. [^ref-cb35a6fb71b2]: Atmel Corporation (2015). ATmega328P Datasheet, 7810D–AVR–01/15, §§6.1, 7.1–7.3, 26.2–26.5 (printed pp. 9, 17–18, 229–231). Manufacturer primary technical documentation, directly inspected; bootloader update support is configuration dependent.