Language Processing Activities

Language processing activity bridges the ideas of software designers with actual execution on the computer system. The designer expresses the idea related to the application domain of the software. To implement these ideas, the description of the ideas has to be interpreted as related to the execution domain of the computer system. The fundamental of language processing activities are grouped into two categories:

1. Program generation activity.
2. Program execution activity.

Program Generation Activity

This activity generates a program from its specification program. Program generation activity bridges the specification gap.

• A program generator is a software system program that accepts the specifications of the program to be generated and generates the program in the target program in a target programming language.
• This activity generates a program from its specification.
• The program generator introduces a new domain between the application and the programming language domain called the program generator domain.
• It accepts the source program and generates a program in the target language.

Program Execution Activity

This activity aims at bridging the execution gap by organizing the execution of a program written in a programming language on a computer system. A program may be executed through translation and interpretation. 

Program Execution Activity

1. This activity involves the actual execution of the program generated by the program generator. The program execution activity bridges the implementation gap.
2. The program execution activity involves loading the program into the memory of the computer system, interpreting the program instructions, and executing them on the computer system.
3. During program execution, the computer system reads the program instructions from memory and executes them one by one, performing the necessary computations and producing the desired results.
4. The program execution activity involves various components of the computer system, including the processor, memory, input/output devices, and other system resources required to execute the program.

In summary, the language processing activities are grouped into program generation activity and program execution activity. The program generation activity generates a program from its specification, while the program execution activity involves the actual execution of the program on the computer system. These two activities are critical for software development and are essential for bridging the gap between the application domain and the programming language domain, as well as the gap between the specification and implementation of software systems.

There are two domains of program execution activity:

1. Program Translation

The program translation model bridges the execution gap by translating a program written in a programming language called the source program into an equivalent program in the machine language called the target program.

• A program must be translated before it can be executed.
• A translated program may save in a file. So that, we can execute saved files or programs repeatedly.

2. Program Interpretation

The interpreter reads the source program and stores it in its memory. Throughout interpretation takes a statement, finds its meaning, and performs actions that implement this. This includes computational and input-output actions. The CPU uses a program counter (PC) to note the address of the next instruction to be executed. 
This Instruction is subjected to the instruction execution cycle consisting of the following steps:

1. Fetch the instruction.
2. Decode the instruction to determine the operation to be performed, and also its operands.
3. Execute the Instruction

At the end of the cycle, the instruction address in PC is updated and the cycle is repeated for the next instruction. 
Program Interpretation can proceed in an analogous manner. Thus, the PC can indicate which statement of the source program is to be interpreted next.