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History of Pascal language

The Pascal language was named for Blaise Pascal, a French mathematician who was a pioneer in the history of computer development. In 1641, at the age of eighteen, Pascal built the first arithmetic machine, probably the first computer. He would improve the instrument eight years later. In 1650, Pascal left the world of geometry and physics to devote himself to religious studies or, as Pascal writes, to "contemplate the greatness and misery of man". Pascal died in Paris on August 19, 1662.

The first computers were programmed in machine code and assembly. This type of programming is tedious and error prone, and extremely difficult to understand and modify. Programming is a long and expensive process. High level languages have been developed to solve this problem. High-level languages provide a set of statements that read like a program called a machine code compiler. Pascal is one of those languages.

Other high-level languages developed during the early years of the computer were FORTRAN (1957), COBOL (1959), Algol (1960), APL (1962), BASIC (1964), C (1972) and Ada ( 1983), in the name of some. A problem with many early languages (eg FORTRAN and BASIC) was the heavy reliance on the use of "goto" instructions. The "Goto" instructions tell the computer to jump from one step to another, allowing the computer to skip the steps or go back to repeat the previous steps. This type of sporadic branching increases the difficulty of the debugging code. In addition, languages such as COBOL have been designed with definitions that are too clear, support for weak data structures, and lack of flexibility, making programs tedious to code and difficult to improve.

Niklaus Wirth completed the development of the original Pascal programming language in 1970. He based it on the block-structured style of the Algol programming language. There were two original goals for Pascal. According to the Pascal standard (ISO 7185), these objectives were to a) make teaching language available as a systematic discipline based on fundamental concepts clearly and naturally reflected in language, and b) to define a language whose implementations could be both reliable and efficient on the computers then available.

Principles of Turbo Pascal

Basic structure of a program

• Description (name of the program). Keyword PROGRAM.
• Main block of instructions, executed sequentially. Key words BEGIN and END. Importance of the. final.
• Importance of indentation.
• Right use of lowercase and uppercase letters.

Sequence of instructions

• Separated by;
• Convention of; at the end of the line.
• Equivalence of spaces and line breaks

The WriteLn statement

• Strings delimited by an apostrophe.
• Simple example: WriteLn (string_of_characters).

   PROGRAM Hello;
   BEGIN
     WriteLn ( 'Hello')
   END.

• Example with multiple arguments separated by commas.

   PROGRAM Hello;
   BEGIN
     WriteLn ('Hello', 'dear user')
   END.

• Example with a variable name as argument.

   PROGRAM Hello;
   VAR Message: STRING;
   BEGIN
     Message: = 'this message';
     WriteLn ('Message', 'worth', Message)
   END.

The assignment to a variable

• Notion of variable (reservation of a box in the memory).
• Importance of the type. The STRING type.
• Declaration of a variable, with VAR.
• Assignment (symbol: =).

The ReadLn instruction

• Assignment by a value at the choice of the user.
• Example of the program that says "hello".

PROGRAM Hello;
VAR Name: STRING;
   BEGIN
     WriteLn ('What is your name?');
     ReadLn (Name);
     WriteLn ('Hello', Name)
   END.

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