Computers: The Ultimate Controller of Modern Life

Every person living today has had their life influenced in some way by computers. Computers influence how we communicate, travel, work, learn, and even think. Because computers are so deeply embedded in modern life, it is no longer acceptable to treat them as mysterious black boxes.

Having a basic understanding of what a computer is and what it does is as fundamental today as knowing the alphabet. It is about understanding the nature of the tool that quietly controls much of the modern world.

Surprisingly, the core idea of a computer is extremely simple.

To understand a computer, we start with behavior.

A computer follows instructions.

At its core, a computer does one thing: it follows instructions.

Imagine you manage people doing many repetitive tasks. Instead of explaining the steps every time, you write each task with their steps on a piece of paper. You number the papers. Now, instead of explaining everything, you simply say: “Do task number 7.” The number refers to a known list of steps.

That is exactly how a computer works.

When a computer receives a number, that number tells it what to do.

Instructions are just numbers.

A computer does not understand words. It only understands numbers.

These numbers use binary notation, where each group of bits consists of 1s (meaning electricity is present) and 0s (meaning electricity is absent). A binary number value represents an instruction.(See blog on binary numbers)

The computer simply interprets the number.

The computer has a built-in list of numbers that define the instructions. Once the computer figures out the value of the binary number, it knows what to do. It then does what the instruction told the processor to do.

Binary instructions come from memory as binary numeric values.

A computer requires a place to hold the binary instructions it needs to execute. That place is memory.

Memory is simply a long list of holding locations, each holding a binary number. Each location has a numeric address, which is also a binary number.

To retrieve an instruction,

• the computer sends a binary address to memory.
• The computer asks for the binary value at that location. The computer knows that it is asking memory for a binary instruction.
• Memory returns the binary number stored at that address. The computer treats that returned number as an instruction.

Computer working with memory to get an instruction

The processor cycle.

The processor repeats the same cycle over and over:

• Fetch: get a binary instruction from memory.
• Decode: figure out what the instruction means.
• Execute: perform the instruction.

After the cycle, the computer moves to get the next instruction.

The cycle repeats while the computer is on.

Instruction order.

In its simplest form, the processor

• starts at a known memory address,
• executes the instruction found there,
• adds one to the address,
• then fetches the next instruction.

This is how instructions are performed in sequence.

The one decision that changes everything.

So far, this describes a very obedient but very dumb machine.

What transforms the computer into the most powerful device ever created is one single ability: the ability to choose the next instruction.

After executing an instruction,

the processor can either continue to the next instruction in memory with the binary address after the one just executed.

or

change the address of the next instruction to a different instruction somewhere else in memory.

This action is known as a jump.

It executes instructions out of sequence under the control of the processor.

That choice depends on the result of the current instruction.

This is how decisions and responsiveness are created.

The simple definition.

A computer executes a binary number as an instruction taken from memory, and then decides which instruction to execute next.

It is that simple. This simple device now controls the world.