Comparison of programming languages (basic instructions)

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Data types

How to declare variable x as the following types:

Integer Unsigned integer Float String
C int x; unsigned int x; float x; or double x; char x[]; or char *x;
C++ (STL) int x; unsigned int x; float x; or double x; string x;
Java int x; float x; or double x; String x;
Pascal var x: integer; var x: word; var x: real; var x: string;
Visual Basic dim x as integer
Python x = value x = value x = value x = "string"
S-Lang x = value x = value x = value x = "string"

Logical cycles

if else if while for i = 1 to N select case
C if (condition) { instructions } else { instructions } if (condition) { instructions } else if (condition) { instructions } while (condition) { instructions } for (i = 0; i<N; i++) { instructions } switch (variable) { case case1: instructions break; ... }
C++ (STL) as above as above as above as above as above
Java as above as above as above as above as above
Pascal if condition then begin \n instructions \n end; if condition then begin \n instructions \n end\n else begin \n instructions \n end; repeat \n instructions \n until condition; for i := 1 to N do \n begin \n instructions \n end; case variable of \n meaning: instructions; \n default: instructions \n end;
Visual Basic if condition then \n instructions \n end if while condition \n instructions \n wend for i = 1 to N step 1 \n instructions \n next
Python if condition : \n \t instructions \n else: \n \tinstructions \n for i in range(1, N): \n \t instructions \n
S-Lang if (condition) { instructions } else { instructions } if (condition) { instructions } else if (condition) { instructions } while (condition) { instructions } for (i = 0; i<N; i++) { instructions } switch (variable) { case case1: instructions } { case case2: instructions } ...

Function declaration

basic value-returning function
C void foo(parameters) { } type foo(parameters) { }
C++ (STL) as above as above
Java public or private + as above public or private +as above
Pascal procedure foo(...); function foo(...):type;
Visual Basic
Python def foo(parameters): \n \t instructions \n add return value at the end.
S-Lang define foo (parameters ; qualifiers) { } define foo (parameters ; qualifiers) { ... return value; }

Data conversions

string to integer string to float integer to string float to string
C integer = atoi(string); float = atof(string); sprintf(string, "%i", integer); sprintf(string, "%f", float);
C++
Java integer = Integer.parseInt(string); float = Float.parseInt(string); string = integer; string = float;
Pascal SysUtils.StrToInt(string); SysUtils.StrToFloat(string); SysUtils.IntToStr((integer); SysUtils.FloatToStr((float);
Visual Basic
Python int('5') float('5.0') str(5) str(5.0)
S-Lang integer = atoi(string); float = atof(string); string = string(integer); string = string(float);

Standard Input and Standard Output

stdin stdout stderr
C scanf( ... );
fscanf(stdin, ... );
printf( ... );
fprintf(stdout, ... );
fprintf(stderr, ... );
C++ cin >> x; cout << x; cerr << x;
Java x = System.in.read(); System.out.print(x); System.err.print(x);
Pascal read( ... ); (or readln( ... );) write( ... ); (or writeln( ... );) var IOResult;
Visual Basic input print x ?
Python
  • For numbers: x = input()
  • For strings: x = raw_input()
print( ... )
sys.stdout.write( string )
sys.stderr.write( string )
S-Lang fgets (&x, stdin) fputs (x, stdout) fputs (x, stderr)

Reading arguments

Argument values Argument counts
C char **argv int argc
C++ as above as above
Java string = args[x]; integer = args.length;
Pascal
Visual Basic
Python sys.argv len(sys.argv)
S-Lang __argv __argc