🧾 What are Punch Cards in Batched Operating Systems?
🧩 The Context:
Before modern keyboards and terminals, computers were fed data and programs physically—and that’s where punch cards come in. This was the norm in early computing (1950s–1970s), especially with batch operating systems.
🏗️ What is a Punch Card?
A punch card is a piece of stiff paper that holds data via holes punched in predefined positions. Each card represented:
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A line of code
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Or a command
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Or data
A stack of cards represented a full program or batch job.
📦 How it worked in Batched OS:
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Users wrote programs (often in languages like FORTRAN or COBOL) and punched them into cards.
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They submitted the stack of cards to the operator.
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The operator collected multiple jobs and loaded them into the system in one go — hence the term batch.
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The OS processed these jobs sequentially, one after the other, without user interaction.
🎯 Key Points:
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Punch cards were input media for early computers.
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They enabled non-interactive (offline) job submission.
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Each batch job was submitted as a deck of punch cards.
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Very error-prone: one misplaced or mispunched card could crash the whole job.
🔁 Legacy?
Modern batch processing (like cron jobs, CI/CD pipelines, etc.) is conceptually descended from this idea: grouping jobs and executing them automatically without manual intervention.
🧠 Interview Line:
“Punch cards were physical input media used in early batch operating systems to submit jobs in bulk for sequential execution without user interaction.”