Some C++ Only Features

• Boolean type
• Classes & Objects
• namespaces and using statements
• exception handling (with try, catch, throw)
• using new and delete for dynamic memory management
• templates
• Function Overloading
• Pass by Reference
• Default Paramenters

The c style implementation of libraries look like # include <stdio.h> There are 4 diffrent styles of casting (static, dynamic, const, and reinterpreted casts)

Declerations

• While declaring arrays, the size of the array should be specified as const or a literal. The size of an array may not be variable

int size =100; int list[size]; - Would NOT work int list[100]; - Would work

Unlike c++, C requires variable declarations at the top of the functions This means that, ALL variables should be declared at the beginning of the function

for (int i=0; i< 10; i++){} // wrong

int i; for(i = 0; i < 10; i++){} // correct

Standard I/O streams stdin:: input stream stdout:: output stream stderr:: error stream

Streams are sequences of characters flowing from one place to another

stdio.h - contains basic I/O functions

Formatied I/O - refers to the conversion of data to and from a stream of characters for printing

scanf: - Reads from standard input (stdin) printf: - writes to standard input (stdout)

Output with printf printf (format_string, list_of_expressions);

• format_string is the layout of whats being printed
• list_of_expressions is a list of comma seperated variables

Specifier	Purpose
%d	int (signed decimal int)
%u	unsigned decimal int
%f	floating point (fixed notation)
%e	floating point (exponential notation)
%s	string
%c	char
%x	Hexidecimal number

• We can specify the field width. Defaults to right-justification (use - for left), we use this syntax:

printf(%10d) - for 10 spaces

Using scanf basics

scanf (format_string, list_of_variable_addresses)

• format string is like that of printf
• But instad of expressions, we need space to store incoming data, hence the list of variable addresses.

int month, day; printf("Please enter birth month, followed by birthday"); scanf(%d %d, &month, &day);

Conversion Specifiers

• Mostly the same for output, Some small diffrence
• Use %f for type float, but use %lf for types double and long double

C Strings char word1[20]; scanf("%s", word1);`

• Similarly you can read a string into a char array with scanf.
• Charecters are read from the keyboard until the first white space, the null character is automatically placed at the end for termination

char greeting[] = "Hello"; printf("%s", greeting); // Prints the word Output: "Hello"

• The format string used for a scanf command is essentially a regular expression
• The data from stdin comes in as a string. The conversion specifier converts the data into the correct "type".
• If we specifiy a particular charecter in the format string, scanf will ignore that character if it occurs at the same spot
• We can also instruct scanf to look for or ignore particular characters
• Example scanf("%25[^*]*%s", str1, str2);

C-Strings dont need the address because the name acts as a pointer to the array

Structs and enums

• C & C++ definitions of a struct are the same
• In C++, declaring a struct or an enum automatically creates a new type
• In C, we need to remind the compiler about the user defined types everytime we use them

We can define a new type in C using typedef

typedef struct student { char name[20]; double gpa; } Student; // now the new type name struct student s1; // C declaration using "tag" Student s2; // C declaration using new type name

Dynamic Memory Allocation

- C does not come with the `new` and `delete` operators. We need to use `malloc` and `free`. - These functions are in `` - The syntax for an array of ints is: `line * arr = (line*) malloc (size_of_array * sizeof(int));`

For an arrau of the line strict, which has been typedef'ed is: line * arr = (line*) malloc (size_of_array * sizeof(line));

[[Computer Science Notes/CDA 3100/Index|Index]]