26.4.1. Instruction Count vs. Instruction Length

Now, why this is no advantage still always? I will tell that; I will take the case of the two word this instruction, because this is also taken 6 and this is also taken as 6, but as I told you here we have kept the format like, A and B and the value is stored in H and using this H as a only destination, but as a homework you can always try and you will find that the number of instructions will reduce.

This section starts by discussing the relationship between the instruction length and instruction count. It states that while two different instruction formats might have the same number of instructions, it's not always advantageous. In the example provided, when using a two-word instruction, the instructor highlights that one format is using a value stored in H as its destination. The suggestion to explore this as homework indicates that students can experiment with instruction formats to understand how instruction counts may vary.

Think of instruction lengths as different ways to write a recipe. A complex recipe might take many detailed steps (similar to a long instruction), while a simpler recipe can be summarized in a few steps (short instruction). However, if you have specific ingredients stored in one place, it might be easier to just reference that location (like pointing to H) rather than listing everything each time.

So, basically this one is actually source destination source. So, now, in this case effectively these two formats have become similar.

The narration goes deeper into the concept of accumulation in instructions. It describes how functions can rely on just one element (the accumulator) to perform tasks that seem similar in both formats. The term 'source destination source' indicates that despite different appearances, the functionality of the instructions may align closely, impacting how many instructions need to be executed.

Imagine you're packing a suitcase. If you pack all your clothes using different compartments (each being a source), it may seem complex. However, if you use just one large compartment (the accumulator), you can fit everything simply. In both cases, the suitcase is full, but the number of actions (or instructions) you'd perform might look very different.

Now, the real class comes. Now, I am taking a single address instruction, now de facto is accumulator everywhere accumulator is de facto. Now, big problem that is in this case; what we have done? we have said that ADD A, B and the store the value of A, C, D value is in C, but if you do not write anything in a single address instruction, then we go with the de facto is accumulator.

In this chunk, the discussion focuses on single-address instructions and their limitations. It narrates how single-address instructions generally use an accumulator as the primary calculation tool. The instruction to 'ADD A, B' implies that the program is adding two variables while noting that if nothing is specified, the fallback is to the accumulator. The challenge arises from having only one accumulator, which can complicate instructions and potentially lead to an increased instruction count.

Consider the accumulator as a single calculator you have at home. If you need to perform multiple calculations (like additions), you have to do each step sequentially and note the results down. If you have to go back and use the previous result for new calculations, it can get quite cumbersome, just like how the number of instructions can increase with more dependency on a single accumulator.

So, therefore, after load A add B and store A, what is going to happen? A is going to have the value of A + B. So, in nutshell what happens I load the value of A in accumulator...

The narrator exemplifies how the operations work sequentially. It describes loading values into the accumulator, performing operations like addition, and then storing the result back into A. This process showcases how multiple steps are necessary to achieve the end result, highlighting the inefficient aspects of single-address instructions where memory must be accessed multiple times.

Imagine you're cooking a dish and separately measuring out your ingredients before combining them in a pot. Each time you measure an ingredient, you have to go back to the shelf and retrieve it. In programming, every time you go back to memory for another piece of information, it's like making another trip to the shelf. The longer the recipe, the more trips you make!