16.5. Execution Process of Programs

These are the 3 Instruction we have designed and the code assigned is your 1, 2 and 5. Other codes are now still available to me. So, now we can design some more Instructions.

The introduction of this section talks about the basic structure of the instruction set for a processor. It mentions that three instructions have already been designed, which are assigned codes 1, 2, and 5. This sets the stage for the creation of additional instructions, indicating the processor's ability to expand its set of operations for better functionality.

Imagine a chef has a base recipe for three different dishes. As they become proficient, they look to create more dishes to offer variety to their menu, showing how they can expand their offerings based on the initial foundation.

Now, we are designing one more Instruction called SUB M. This instruction means that the Accumulator is equal to Accumulator minus contents of Memory.

The instruction named 'SUB M' is introduced, which performs subtraction. Specifically, it updates the Accumulator by subtracting a value stored in memory. This highlights an essential operation on data held in memory and demonstrates how the processor modifies the state of the Accumulator based on input from its memory.

Consider managing a bank account; if you have a certain amount saved in your account (the Accumulator) and make a withdrawal (the contents of Memory), your new balance will be the old balance minus the withdrawal amount, just like the Accumulator reflects a new state after performing the subtraction.

The Instruction format is the same whatever we are going to design for all the Instruction it is going to follow this particular pattern.

This statement addresses the uniformity of the instruction format that will be used for all new instructions. Consistency in format allows for easier decoding by the processor, which is crucial for efficient operation. A consistent pattern reduces complexity in programmed logic.

Think of having a standardized form for filling out applications at a school; every form has the same sections (like Name, Age, Grade). This consistency allows staff to process all applications more efficiently, similarly to how a processor handles instructions.

Now again I am going to give designing 4 more Instruction. This is a similar Instruction load 199 store sub m, but my reference is different. Initially, we are talking about the memories now we are talking about the Registers.

At this point, the focus shifts from memory operations to operations involving registers. Registers are small storage locations in the CPU used for quick access to data. The text indicates a transition in design where new instructions will allow operations directly with registers, emphasizing speed and efficiency in processing.

Think of registers like a notepad on a desk where you jot down quick reminders versus using a filing cabinet (memory) for storing extensive records. Registers enable quick access to important information without the delay of digging through more extensive data storage.

If I say that this is your opcode is your 9000 means it is going to refer to this particular Register 𝑅0. The value of the Register 𝑅0 will be loaded to the Accumulator.

The opcode is a unique binary code that specifies an operation that the processor should perform. For instance, the opcode 9000 refers to the first register, R0, and states that its contents should be loaded into the Accumulator. This process links the instructions to their corresponding actions.

Imagine each opcode is like a remote control button designated for specific tasks, like turning on the TV or changing the channel. Pressing the button leads to a predetermined action—in this case, loading data into the Accumulator.

This Instruction is basically nothing but Accumulator is equal to Accumulator + R7, we are referring to this particular Register.

This chunk discusses how the processor can perform addition operations using registers. The instruction states that the Accumulator's value will be increased by the value stored in register R7. This exemplifies other commercial arithmetic operations that the processor can execute in addition to subtraction.

When budgeting for a party, if you first have $100 (the Accumulator) and receive$50 from a friend (R7), the new total will be $150. The operation takes the initial amount and adds to it, similar to how the Accumulator works in this case.

Now, opcode 0 is your JMP. It is a jump Instruction. It is a halt Instruction; that means, it is going to say that halting the program or stopping the program execution.

Jump instructions are critical for controlling the flow of a program. The JMP instruction allows the processor to move from one part of the program to another directly. The halt instruction is essential for terminating execution correctly and gracefully.

Think about a train system; a jump instruction is similar to a train switching tracks to reach a different destination. A halt is like the train finally reaching its station and stopping, signaling that the ride is complete.