How was the first computer software created, without computer software to create it?
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Computer software is, like everything else computers do, fundamentally just data stored in the computer’s memory. Since that data physically exists as a physical object, you can manually set it up by manually flipping each of the necessary bits in some form of storage. (For the earliest computer programs, this storage was typically punchcards, where bits were “flipped” by either punching or not punching each slot in the card.)
To expand on this a little in terms of how data becomes actions: each computer processor has something called an *instruction set*. These instructions are extremely basic: things like “get the data found at a particular memory address” or “add two numbers”, and they’re physically built into the actual hardware of the processor. Each of these instructions is represented by a numerical value, called an *opcode*.
With each step in the processor’s operation, the hardware inside the processor effectively takes the opcode and compares it to each of the built-in operations it can do via a bunch of logic gates. Only the circuit matching the opcode actually becomes active, and that circuit, via its hardware, actually executes the instruction.
So, to write a computer program, all you fundamentally need is a very long list of opcodes, physically encoded into the computer’s memory. This is a very unwieldy way to program, but you *can* do it. And more importantly, you can string together a bunch of opcodes that write a program that reads more human-readable data and *translates* it into opcodes, you can start writing code in more human-readable ways. Such a program, called a *compiler*, was one of the earliest innovations in computing.
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In modern computers, we still run this basic program, only it’s physically built in to a tiny bit of memory on the motherboard. When you turn the computer on, it executes that tiny stored program, typically a [BIOS](https://en.wikipedia.org/wiki/BIOS), which is then used to start reading other memory and to start the operating system.
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