• Blogs
• Universial Tech
• Instructions Drive The Computing Process

If hardware is the body of the computer, software tells that body what to do.

At its most basic level, software is nothing more than a list of binary instructions stored in memory. To understand software, we must first understand what an instruction is.

The Binary Instruction

The processor (CPU) does not think. It does not understand meaning. It only executes instructions.

An instruction tells the processor what action to perform. An instruction represents a number in binary form. The value of that number tells the processor what to do.

Designers build every processor with a list of such numbers, each representing an action the processor knows how to perform. This list is called the instruction set.

For example, imagine a processor that understands 200 possible instructions. Let us say instruction number 37 means ADD.

But adding requires more than just the word 'add.' The processor must also know:

• What two numbers to add
• Where those numbers are located (sources)
• Where to place the result (destination)

So an instruction must contain:

• The operation (Add)
• Source A (first number)
• Source B (second number)
• Destination (where to store the result)

Binary numbers represent both the actual information and the memory address where that information is stored. The processor simply interprets these binary patterns according to its built-in design.

Memory Holds Everything

Memory stores binary values. Some of those values represent instructions, while others represent data.

The processor interacts with memory using binary numbers as addresses. An address identifies a specific memory location.

The processor gets (reads) binary data from memory and puts (writes) binary data into memory. When it needs an instruction, it places a binary number on the memory address lines and receives the instruction stored at that location.

Memory becomes the holding place for instructions, data, and results. Everything inside the computer is represented as binary.

Illustration: A Simple Program in Memory

Below is a simplified view of how a small program might appear inside memory.

In this example, address 100 contains an ADD instruction. It adds the values stored at addresses 120 and 121 and places the result at address 122.

After executing address 100, the processor moves to address 101. It continues step by step unless an instruction changes the direction.

Types of Instructions

• Math: Add, Subtract, Multiply, Divide
• Logical: AND, OR, NOT
• Data Movement: Load, Store, Copy
• Test / Decision: Compare values and change direction

Regular instructions move forward in sequence. Test instructions can change which instruction executes next. This ability to change direction allows programs to make decisions.

Organizing Instructions: The Role of the Programmer

A single instruction cannot accomplish anything meaningful by itself. To achieve anything significant, the processor must execute a series of instructions arranged in a specific order.

A programmer understands the task at hand and organizes the instructions in the correct sequence to accomplish it.

In its most primitive form, the programmer writes instructions in a cryptic language that directly represents the processor’s instruction set. The programmer:

• decides which instructions will be stored in memory
• decides where the data will be placed in memory
• decides where the results will be stored in memory

Each instruction must ultimately be represented in binary so the processor can execute it.

Placing the sequence of instructions into memory is called loading the program.

Running the Program

Once the binary instructions and data are loaded into memory, the programmer tells the processor the address of the first instruction.

The processor begins executing that instruction, and each instruction leads to the next unless a test instruction directs it elsewhere.

The sequence of instructions that accomplishes a purpose is called a program. A program means performing actions in a predetermined order. Starting execution of those instructions is called running the program.

The Primitive Truth

At its simplest level, software is a sequence of binary instructions stored in memory that directs the processor to perform actions.

Nothing more. Everything else—applications, operating systems, and even artificial intelligence—is built upon this simple foundation.