History of C Programming Language
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What was the original goal of the American National Standards Institute (ANSI) committee established in 1983 related to the C programming language?

  • To produce an ambiguous definition of the language C
  • To produce an unambiguous and machine independent definition of the language C (correct)
  • To produce a machine-dependent definition of the language C
  • To establish a committee to oversee the development of C++ language

    • Which programming language was UNIX primarily written in?

  • C++
  • C (correct)
  • Java
  • Assembly Language

    • What makes UNIX one of the first portable operating systems?

  • It was specifically designed for DEC PDP-11 computers
  • The majority of the code does not know or care about the computer it is running on (correct)
  • It relies heavily on specific hardware architecture
  • Machine-specific features are scattered throughout the UNIX code

    • Who originally designed the C programming language for use with UNIX on DEC PDP-11 computers?

    <p>Dennis Ritchie</p> Signup and view all the answers

    Which book was the first publication about the C programming language, authored by Brian Kernighan and Dennis Ritchie?

    <p>The C Programming Language</p> Signup and view all the answers

    What was one of the earlier forms of the C language before it evolved from B?

    <p>BCPL</p> Signup and view all the answers

    What is the purpose of local declarations in a C program?

    <p>To declare variables inside a given function or block</p> Signup and view all the answers

    Which of the following statements is considered part of a C program?

    <p>switch, case</p> Signup and view all the answers

    In C programming, what is the purpose of user-defined functions?

    <p>To specify operations as needed by the user</p> Signup and view all the answers

    What is the role of the return function in C programs?

    <p>To end the execution of a function</p> Signup and view all the answers

    Why must every file containing a C program be saved with a '.c' extension?

    <p>To allow linking with library functions</p> Signup and view all the answers

    What is the purpose of the linker in C programming?

    <p>To link object files with library functions</p> Signup and view all the answers

    Which component loads the executable file into RAM during program execution?

    <p>Loader</p> Signup and view all the answers

    What does the Instruction Register do during program execution?

    <p>Holds the current instructions for CPU execution</p> Signup and view all the answers

    'Program Counter' in C programming is responsible for:

    <p>Holding the address of the next instruction to be executed</p> Signup and view all the answers

    What does the Accumulator store during program execution in C programming?

    <p>Information related to calculations</p> Signup and view all the answers

    What is the name of the recognized standard for C language established by ANSI?

    <p>ANSI C</p> Signup and view all the answers

    Which organization established a standard for C similar to ANSI C?

    <p>ISO</p> Signup and view all the answers

    What is the primary advantage of using C for writing programs?

    <p>Efficiency and portability</p> Signup and view all the answers

    Which section of a C program includes program's name, date, and description?

    <p>Documentation section</p> Signup and view all the answers

    What purpose does the preprocessor section serve in a C program?

    <p>Link header files to system libraries</p> Signup and view all the answers

    Which keyword is used to declare constants in the define section of a C program?

    <p>#define</p> Signup and view all the answers

    What is the purpose of the main function in a C program?

    <p>To start program execution</p> Signup and view all the answers

    'void main()' versus 'int main()' in C programming primarily differs in:

    <p>Returned value type</p> Signup and view all the answers

    Why is C considered well-suited for writing both system and application software?

    <p>Availability of several data types and operators.</p> Signup and view all the answers

    What is the output of the following code snippet?

    #include int main() {
    int a, b, sum;
    printf("Enter two no: ");
    scanf("%d %d", &amp;a, &amp;b);
    sum = a + b;
    printf("Sum : %d", sum);
    return(0);
}

    Given Input: 3 7

    <p>Enter two no: Sum : 10</p> Signup and view all the answers

    What does the C function 'ceil(number)' do?

    <p>Rounds up the given number to the nearest integer</p> Signup and view all the answers

    Which of the following is NOT a C keyword?

    <p>print</p> Signup and view all the answers

    What does the 'pow(base, exponent)' function do in C?

    <p>Returns the power of the given number</p> Signup and view all the answers

    In C programming, what do identifiers refer to?

    <p>Names of variables and program elements like functions</p> Signup and view all the answers

    What is an essential requirement for declaring identifiers in C programming?

    <p>Not being a reserved keyword</p> Signup and view all the answers

    What is the purpose of assigning values to variables in a C program?

    <p>To store and manipulate data during program execution</p> Signup and view all the answers

    'sizeof' is an example of which of the following in C programming?

    <p>'C' operator to determine memory consumption</p> Signup and view all the answers

    'int_amt=(prt)/100;' in C programming is an example of what?

    <p>Assignment operation with arithmetic expression</p> Signup and view all the answers

    Which function in C programming rounds down a given number?

    <p>floor(number)</p> Signup and view all the answers

    Which type of variable retains its value between multiple function calls?

    <p>Static variable</p> Signup and view all the answers

    What is the default visibility scope of automatic variables in C?

    <p>Local</p> Signup and view all the answers

    In C, where must global variables be declared?

    <p>Outside any function or block</p> Signup and view all the answers

    What is the purpose of the static keyword when declaring a variable in C?

    <p>To retain the variable's value between function calls</p> Signup and view all the answers

    Which storage class is associated with automatic variables in C?

    <p>Auto</p> Signup and view all the answers

    What is the default lifetime of static variables in C?

    <p>Till the end of the main program</p> Signup and view all the answers

    Which symbol is not allowed to start a variable name in C?

    <h1>(hash)</h1> Signup and view all the answers

    'int long' is an invalid variable name in C because:

    <p>'int long' is a reserved keyword in C.</p> Signup and view all the answers

    'extern int x=10;' declares an external variable with an initial value. Why might this declaration cause issues?

    <p>'extern' variables should not be explicitly initialized.</p> Signup and view all the answers

    Which data type is used to store the address of a variable in C?

    <p>Pointer data type</p> Signup and view all the answers

    What is the range of an unsigned char data type in C?

    <p>0 to 255</p> Signup and view all the answers

    Which of the following is an example of a derived data type in C?

    <p>Array</p> Signup and view all the answers

    What is the purpose of using typedef in C?

    <p>To create new variable names</p> Signup and view all the answers

    What do escape sequences represent in C?

    <p>Control characters like newline, tab</p> Signup and view all the answers

    Which type of constant allows for increasing the storage range in C?

    <p>Unsigned constant</p> Signup and view all the answers

    'I am a little boy' would be classified as:

    <p>'I' string constant</p> Signup and view all the answers

    'typedef int Integer;' statement creates a synonym for which data type?

    <p>'int'</p> Signup and view all the answers

    Which storage class in C allows variables to hold their value between multiple function calls?

    <p>Static</p> Signup and view all the answers

    In C, which storage class allows variables to be stored in the CPU registers?

    <p>Register</p> Signup and view all the answers

    What happens if you try to dereference a register variable in C?

    <p>It is not allowed and will result in a compilation error</p> Signup and view all the answers

    What does the extern storage class declaration indicate in C?

    <p>Variable is declared elsewhere with external linkage</p> Signup and view all the answers

    What does the compiler do if an extern variable in C is not initialized within the program?

    <p>Searches for it to be initialized somewhere in the program</p> Signup and view all the answers

    Study Notes

    History of C

    • The C language was first proposed in 1972 by Dennis M. Ritchie at Bell Laboratories, USA.
    • In 1983, the American National Standards Institute (ANSI) established a committee to standardize the definition of C, resulting in ANSI C.
    • ANSI C is the recognized standard for the language, grammar, and core set of libraries.

    Characteristics of C

    • C is a robust language with a rich set of built-in functions, data types, and operators.
    • Programs written in C are efficient due to the availability of several data types and operators.
    • C is a highly portable language, allowing code written on one machine to be easily moved to another.
    • C supports low-level features like bit-level programming and direct access to memory using pointers.

    Basic Structure of a C Program

    • A C program consists of several sections, including:
      • Documentation section (includes comments and program description)
      • Preprocessor section (includes header files and library links)
      • Definition section (includes constants and macros)
      • Global declaration section (includes global variables and functions)
      • Main function (the entry point of the program)
      • User-defined functions (custom functions written by the programmer)

    Program Execution

    • When a C program is compiled and executed, the compiler generates several files, including:
      • Source file (with a .c extension)
      • Object file (with a .obj extension)
      • Executable file (with a .exe extension)
    • The program is executed in the following steps:
      1. The loader loads the executable file into RAM and informs the CPU of the starting point.
      2. The CPU executes the program, using the Instruction Register and Program Counter.

    C Math Functions

    • C provides several math functions, including:
      • ceil() (rounds up a number)
      • floor() (rounds down a number)
      • sqrt() (returns the square root of a number)
      • pow() (returns the power of a number)
      • abs() (returns the absolute value of a number)

    C Tokens

    • Tokens are the individual units of a C program, including:
      • Keywords (reserved words with specific meanings)
      • Identifiers (names of variables, functions, and arrays)
      • Constants (numeric, character, or string values)
      • Operators (symbols used for arithmetic, comparison, and logical operations)
      • Punctuators (symbols used for grouping and separating tokens)

    Keywords

    • Keywords are reserved words in C, including:
      • auto
      • double
      • int
      • struct
      • break
      • else
      • long
      • switch
      • ...

    Identifiers

    • Identifiers are names of variables, functions, and arrays, and must follow certain rules:
      • Can be named from a combination of A-Z, a-z, 0-9, and _
      • First character must be an alphabet or underscore
      • Must not be a keyword
      • Can be up to 31 characters long

    Data Types

    • C provides several data types, including:
      • int
      • float
      • char
      • double
      • long
      • short
      • unsigned
      • ...

    Variables

    • Variables are named storage locations that can hold different values, and can be:
      • Local (declared inside a function or block)
      • Global (declared outside a function or block)
      • Static (retains its value between multiple function calls)
      • Automatic (allocated memory automatically at runtime)
      • External (shared across multiple C source files)

    Storage Classes

    • Storage classes in C determine the lifetime, visibility, memory location, and initial value of a variable, including:
      • Automatic
      • External
      • Static
      • Register### C Data Types
    • C supports four classes of data types: basic, derived, user-defined, and pointer data types.

    Basic Data Types

    • Basic data types support arithmetic operations such as addition and subtraction.
    • Examples: int a, b;, char c;
    • Storage size and range of basic data types:
      • Unsigned char: 8 bits, 0 to 255
      • Char: 8 bits, -128 to 127
      • Short int: 16 bits, -32768 to 32767
      • Unsigned int: 32 bits, 0 to 4294967295
      • Int: 32 bits, -2147483648 to 2147483648
      • Unsigned long: 32 bits, 0 to 4294967295
      • Enum: 16 bits, -2147483648 to 2147483648
      • Long: 32 bits, -2147483648 to 2147483648
      • Float: 32 bits, 3.4e-38 to 3.4e38
      • Double: 64 bits, 1.7e-308 to 1.7e308
      • Long double: 80 bits, 3.4e-4932 to 1.1e4932

    Derived Data Types

    • Derived data types store a set of data values.
    • Examples: arrays and structures.

    User-Defined Data Types

    • C provides a facility called typedef for creating new data type names defined by the user.
    • Example: typedef int Integer; makes Integer a synonym of int.

    Pointer Data Types

    • Pointer data types store the address of a variable.

    Constants

    • A constant is a quantity that does not vary during the execution of a program.
    • Two types of constants: numeric and character constants.

    Numeric Constants

    • Examples: 786, -127, 1234567899L (long constant)
    • Unsigned constants: 123456789u (unsigned constant), 1234567891ul (unsigned long constant)
    • Advantage of declaring an unsigned constant: increases the range of storage.
    • Floating-point constants: 123.4, 1e-2, 1.4E-4

    Character Constants

    • A character constant is written as one character within single quotes, e.g. 'a'.
    • Escape sequences: \a (alert), \b (backspace), \f (form feed), \n (new line), \r (carriage return), \t (horizontal tab), \v (vertical tab)

    String Constants

    • A string constant is a sequence of zero or more characters surrounded by a double quote, e.g. " I am a little boy".
    • Quotes are not part of the string.

    Enumeration Constants

    • An enumeration constant is a list of constant integer values, e.g. enum color { RED, Green, BLUE }.
    • The first name in the enum has the value 0, and the next 1, and so on unless explicit values are specified.

    Variables

    • auto variables: default initial value is garbage.
    • static variables:
      • Hold their value between multiple function calls.
      • Visible only to the function or block in which they are defined.
      • Can be declared many times but can be assigned at only one time.
      • Default initial value of static integral variables is 0 otherwise null.
    • register variables:
      • Allocated memory into the CPU registers.
      • Can not be dereferenced (i.e., can not use & operator).
      • Access time is faster than automatic variables.
      • Initial default value of register local variables is 0.
      • Can store pointers into the register.
    • extern variables:
      • Used to tell the compiler that the variable is declared with an external linkage elsewhere in the program.
      • Not allocated any memory.
      • Default initial value of external integral type is 0 otherwise null.
      • Can only initialize the extern variable globally.
      • Can be declared many times but can be initialized at only once.

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    Explore the evolution and milestones of the C programming language, which originated at Bell Laboratories in 1972. Learn about the standardization efforts by ANSI and its association with UNIX.

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