Instruction, sequential programming

The sequence of instructions to be executed by the computer is called a program. In actuality, the program is a set of binary-coded instructions stored in memory. The CPU fetches each instruction from memory, interprets and executes it, and then moves on to the next instruction. The CPU fetches instructions sequentially from memory, unless told to do otherwise by one of the instructions. 

SISD machines call for the concept of sequential programming in which a program consists of a list of instructions to be executed one after the other. Although such machines may now work so fast that they appear to be executing more than one instruction at a time, the sequential programming paradigm still remains for most techniques and tools for software development, including sound synthesis. 

A very simple illustration in which information from two inputs is dealt with sequentially (serially) by a microprocessor. Input 1 is accepted, and the left-hand series of instructions (program 1) are carried out. Then, Input 2 is examined, and the right-hand set of instructions is followed through. The processes are iterated. If each program (1, 2) takes 1 msec, the total time for one iteration is 2 msec. 

We assume that our program scheme P is written in linear sequential form with the first instruction in line 1. We use the convention that in a test statement the first transfer address is the transfer for positive (TRUE) outcome of the test. We can assume that P has input variables x, ...,x disjoint from program variables, ...,ym and an output variable z which is neither an input for a program variable and only appears in a halting sequence z + u STOP. 

Turing Machine (TM) is driven by a program which is interpreted by its Control Unit (CUTM). The Control Unit CUTM is a finite automaton (Mealy s or Moore s sequential machine). The program for the TM consists of the finite sequence rj of instructions jj j... 

Conventional CPUs found in the majority of modern computers, such as those manufactured by Intel and advanced micro devices (AMD), are designed for sequential code execution as per the Von Neumann architecture [16]. While running a program, the CPU fetches instructions and associated data from the computer s random access memory (RAM), decodes it, executes it, and then writes the result back to the RAM. Within the realm of Flynn s taxonomy [17], this would be classified as single instruction, single data (SISD). 

For any CNC machine to operate, it must be provided with information regarding the operations it will be required to perform. This information is provided by a part program, which is a series of step-by-step instructions, written in sequence, in a format which the machine control system will read, interpret and execute. The control system will first read, interpret and execute the very first command in the program. Only then will it go to the next command then read, interpret and execute. The control will then continue to execute the program commands in sequential order until it reaches the end of program. 

An automated process is any set of tasks that has been combined to be carried out in a sequential order automatically and on command. The tasks are not necessarily physical in nature, although this is the most common circumstance. The execution of the instructions in a computer program represents an automated process, as does the repeated execution of a series of specific welds in a robotic weld cell. The two are often inextricably linked, as the control of... 

The strategy used to remedy this problem is called memory hierarchy. Memory hierarchy works because of the locahty property of memory references due to the sequentially fetched program instructions and the conjugation of related data. In a hierarchical memory system there are many levels of memory hierarchies. A small amount of very fast memory is usually allocated and brought right next to the central processing unit to help match up the speed of the CPU and memory. As the distance becomes greater between the... 

One reason that RISC architectures work better than traditional CISC machines is due to the use of large on-chip caches and register sets. Since locality of reference effects (described in the section on memory hierarchy) dominate most instruction and data reference behavior, the use of an on-chip cache and large register sets can reduce the number of instructions and data fetched per instruction execution. Most RISC machines use pipelining to overlap instruction execution, further reducing the clock period. Compiler techniques are used to exploit the natural parallelism inherent in sequentially executed programs. 

Firstly, we introduce the following definition. A basic block is a sequence of instructions i, 2, , > 1), program executes from %i to iu sequentially. 

Easy to program with fill-in-the blanks function blocks plus simple ladder logic or sequential logic instructions. Program language should be as close as possible to the type in use for basic control PLCs. 

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