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https://github.com/pmachapman/LittleC

A modified version of the LittleC Interpreter from Herbert Schildt's C: The Complete Reference (4th Ed.)
https://github.com/pmachapman/LittleC

c interpreter multi-platform

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A modified version of the LittleC Interpreter from Herbert Schildt's C: The Complete Reference (4th Ed.)

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README 

        
# Little C 

The Little C Interpreter from Herbert Schildt's C: The Complete Reference (4th Ed.)



## Table of Contents 



- [Project Structure](#project-structure)

- [Specifications](#specifications)

- [Restrictions](#restrictions)

- [Library Functions](#library-functions)

- [Example Programs](#example-programs)



## Project Structure



The files for this project are in the following directories:



    .

    ├── bcb3                  # Borland C++ Builder 3.0 Project Files

    ├── bcc55                 # Borland C++ Compiler 5.5 Makefile

    ├── clang                 # Clang C Compiler Makefile

    ├── dev-cpp               # Dev-C++ 4.9 Project Files

    ├── gcc                   # Gnu C Compiler Makefile

    ├── qc25                  # Microsoft Quick C 2.5 Makefile

    ├── src                   # Project Source Code

    ├── vc152                 # Visual C++ 1.52 Project File

    ├── vc2                   # Visual C++ 2.0 Project File

    ├── vc42                  # Visual C++ 4.2 Project File

    ├── vc5                   # Visual C++ 5.0 Project File

    ├── vc6                   # Visual C++ 6.0 Project File

    ├── vs2002                # Visual Studio .NET Project File

    ├── vs2003                # Visual Studio .NET 2003 Project File

    ├── vs2005                # Visual Studio 2005 Project File

    ├── vs2008                # Visual Studio 2008 Project File

    ├── vs2010                # Visual Studio 2010 Project File

    ├── vs2012                # Visual Studio 2012 Project File

    ├── vs2013                # Visual Studio 2013 Project File

    ├── vs2015                # Visual Studio 2015 Project File

    ├── vs2017                # Visual Studio 2017 Project File

    ├── vs2019                # Visual Studio 2019 Project File

    ├── vs2022                # Visual Studio 2022 Project File

    ├── watcom                # Open Watcom 1.9 Project File

    ├── xcode                 # Apple Xcode Project File

    ├── LICENSE.md

    └── README.md



## Specifications

The following features are implemented:



 * Parameterized functions with local variables

 * Recursion

 * The **if** statement

 * The **do-while**, **while**, and **for** loops

 * Local and global variables of type **int** and **char**

 * Function parameters of type **int** and **char**

 * Integer and character constants

 * String constants (limited implementation)

 * The **return** statement, both with and without a value

 * The **break**, **continue** and **end** statements

 * A limited number of standard library functions

 * These operators: +, –, *, /, %, <, >, <=, >=, ==, !=, unary –, and unary +

 * These escaped characters: \a, \b, \f, \n, \r, \t, \v, \\', \\", and \\\\

 * Functions returning integers

 * /* ... */-style comments

 * C++ style comments



## Restrictions



The targets of **if**, **while**, **do**, and **for** must be blocks of code surrounded by beginning and ending curly braces. You cannot use a single statement. For example, code such as this will not correctly interpreted:



```C

for(a=0; a < 10; a=a+1)

  for(b=0; b < 10; b=b+1)

    for(c=0; c < 10; c=c+1)

      puts ("hi");



if(a=c)

  if(a=b) x = 10;

```



Instead, you must write the code like this:



```C

for(a=0; a < 10; a=a+1) {

  for(b=0; b < 10; b=b+1) {

    for(c=0; c < 10; c=c+1) {

      puts("hi");

    }

  }

}

if(a=c) {

  if(a=b) {

    x = 10;

  }

}

```



Prototypes are not supported. All functions are assumed to return an integer type (**char** return types are allowed, but elevated to **int**), and no parameter type checking is performed.



All local variables must be declared at the start of a function, immediately after the opening brace. Local variables cannot be declared within any other block. The following function is invalid:



```C

int myfunc()

{

  int i; /* this is valid */

  if(1) {

    int i; /* this is not valid */

    /*...*/

  }

}

```



All functions must be preceded by either an **int** or **char** type specifier. For example, this declaration is valid:



```C

int main()

{

  /*...*/

}

```



However, this one is not:



```C

main ()

{

  /*...*/

}

```



## Library Functions



The following library functions are implemented:



```C

int getche(void);    /* Read a character from keyboard and return its value */

int putch(char ch);  /* Write a character to the screen */

int puts(char *s);   /* Write a string to the screen */

int getnum(void);    /* Read an integer from the keyboard and return its value */

int print(char *s);  /* Write a string to the screen */

int print(int i);    /* Write an integer to the screen */

```



## Example Programs



A program demonstrating all of the features of Little C:



```C

/* Little C Demonstration Program #1.



   This program demonstrates all features

   of C that are recognized by Little C.

*/



int i, j;   /* global vars */

char ch;



int main()

{

  int i, j;  /* local vars */



  puts("Little C Demo Program.");



  print_alpha();



  do {

    puts("enter a number (0 to quit): ");

    i = getnum();

    if(i < 0 ) {

      puts("numbers must be positive, try again");

    }

    else {

      for(j = 0; j < i; j=j+1) {

        print(j);

        print("summed is");

        print(sum(j));

        puts("");

      }

    }

  } while(i!=0);



  return 0;

}



/* Sum the values between 0 and num. */

int sum(int num)

{

  int running_sum;



  running_sum = 0;



  while(num) {

    running_sum = running_sum + num;

    num = num - 1;

  }

  return running_sum;

}



/* Print the alphabet. */

int print_alpha()

{

  for(ch = 'A'; ch<='Z'; ch = ch + 1) {

    putch(ch);

  }

  puts("");



  return 0;

}

```



A program demonstrating nested loops:



```C

/* Nested loop example. */

int main()

{

  int i, j, k;



  for(i = 0; i < 5; i = i + 1) {

    for(j = 0; j < 3; j = j + 1) {

      for(k = 3; k ; k = k - 1) {

        print(i);

        print(j);

        print(k);

        puts("");

      }

    }

  }

  puts("done");



  return 0;

}

```



A program demonstrating the assignment operator:



```C

/* Assigments as operations. */

int main()

{

  int a, b;



  a = b = 10;



  print(a); print(b);



  while(a=a-1) {

    print(a);

    do {

       print(b);

    } while((b=b-1) > -10);

  }



  return 0;

}

```



A program demonstrating recursive functions:



```C

/* This program demonstrates recursive functions. */



/* return the factorial of i */

int factr(int i)

{

  if(i<2) {

    return 1;

  }

  else {

     return i * factr(i-1);

  }

}



int main()

{

  print("Factorial of 4 is: ");

  print(factr(4));



  return 0;

}

```



A program demonstrating function arguments:



```C

/* A more rigorous example of function arguments. */



int f1(int a, int b)

{

  int count;



  print("in f1");



  count = a;

  do {

    print(count);

  } while(count=count-1);



  print(a); print(b);

  print(a*b);

  return a*b;

}



int f2(int a, int x, int y)

{

  print(a); print(x);

  print(x / a);

  print(y*x);



  return 0;

}



int main()

{

  f2(10, f1(10, 20), 99);



  return 0;

}

```



A program demonstrating loop statements:



```C

/* The loop statements. */

int main()

{

  int a;

  char ch;



  /* the while */

  puts("\aEnter a number: ");

  a = getnum();

  while(a) {

    print(a);

    print(a*a);

    puts("");

    a = a - 1;

  }



  /* the do-while */

  puts("enter characters, 'q' to quit");

  do {

     ch = getche();

  } while(ch !='q');



  /* the for */

  for(a=0; a<10; a = a + 1) {

     print(a);

  }



  return 0;

}

```