Strings
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Strings

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Strings Strings Presentation Transcript

  • STRINGSName :- Mandeep kaurClass:- n1Roll no.:- 115322
  • INTRODUCTION OF STRING► Incomputer programming, a string is traditionally a sequence of characters, either as a literal constant or as some kind of variable A string is as a data type and is often implemented as a byte (or word) array that stores a sequence of elements, typically charactersusing some character encoding
  • STORING STRING► Inc++ language,a string is stored in an array of characters.It is terminated by the null (‘0’) character.because string is stored in an array,the name of the aaray, and hence string, is a pointer to the beginning of the string.For example “hello”
  • String Operations►A number of additional operations on strings commonly occur in the formal theory .
  • String Datatype►A string datatype is a datatype modeled on the idea of a formal string . Strings are such an important and useful datatype that they are implemented in nearly never programming language .In some language they are avalible as primitive types and in others as composite types
  • String Literals ►A string literal ,also known as string constant ,is a sequence of charactersenclosed in double quotes.For example:- “hello!you are welcome” “” “a”
  • String Variables► A string variable is actually an array of characters.It has two types3. Declaring string variables4. Initializing string variables
  • STRINGS AND ASSIGNMENT OPERATOR► String is an array of characters , therefore, the name of the array is a pointer constant , it is an rvalue, and therefore cannot be used as the left operand of the assignment operator.► For example :- char strl[]= “hello”; char str2[20]; str2=str1;
  • String lenght► Although formal strings can have an arbitrary length, the length of strings in real languages is often constrained to an artifical maximaum . In general, there are two types of string data type . Fixed length strings , which have a fixed maximun length and which use the same amount of memory .whether this maximum is reached or not , and variable length strings,whose length is not arbitrarity fixed and which use varyingamounts of memory depending on their actul size
  • Character string functions► Stringfunction are used to manipulate a string or change or edit the contents of a string. They also are used to query information about a string.they are usully used within the content of a computer programming language
  • Input/Output of String DataThere are approaches to perform input/output of string data.these are two types:- using character I/O functions using string I/O functions The input/output of string data can be performed using character I/O functions as illustrated in the following programs .
  • Program to perform input/output of string data withcharacter I/O functions of streams objects cin &cout► #include<iostream.h>► Void main()► {► Char str[30];► Int I,n=0;► Cout<<“n enter string of length <=29”;► Cout<<“n and terminate with ENTER keynn”;► While( (str[n]=cin.get() )!=‘n’)► N++;► Str[n]=‘0’► Cout<<“n you have entered nn”;► For(i=0;i<n;i++)► Cout.put(str[i]);► Cout<<“n”;► }
  • Progarm to perform input/output of string data with getline()function of cin stream object► #include<iostream.h>void main►{► Char str[30];► Cout<<“n enter string of length<=29;► Cout<<“n and terminate with ENTER keynn”;► Cin.getline(str,30);► Cout<<“n you have entered nn”;► Cout<<str;► Cout<<“n”;►}
  • The strlen() function:-This function takes one argumentthat can be a string constant or a variable. The counts the no. of character presentin the string. Do remember that null character ‘0’ isnot a part of the character, it is merely used to mark the end of the string,so it is not counted
  • The strcat() function► This function takes two arguments, of which first is a variable and second can be a string constant or a variable. It appends the character(s) of the second arguments at the end of the first argument. There must be sufficient avaible to accommodate the incoming character from destination string,otherwise over flow occurs.
  • Program to illustrate the useof strcat()function► #include<iostream.h>► #include<string.h>► Void main()► {► Char str[30]=“wel”, str2[30]=“come”;► Cout<<“n first string is “<<str1;► Cout<<“nn second string after appending second one is nn”;► Cout<<str<<“n”;► }
  • The strcpy() function► Thisfunctions takes two arguments, of which first is a string variable and second can be a string constant or a variable. It copies the characters of the second argument to the first argument.
  • The strcmp() function► This functions takes two arguments, of which boyh can be string variables or constants.It compares the characters of each but one at a time and returns a value indicating the result of the comparison.► For example:-strcmp(str1,str2);
  • Passing string to a function►A string can be passed as an argument to a function using subscripted notation for arrays.In a function definition, the formal parameter is delared as an array of cahracters.
  • Program to illustrate the passing of a string to a function► #include<iostream.h>► #include<string.h>► Void func(char[]); //function prototype► Void main()► {► Char str1[]=“sample string’;► Func(str1);► }► Void func(char temp[])► {► Cout<<“n string passed to it:”<< temp;► Cout<<“nn its length is:”<<strlen(temp)<<“n”;► }
  • Array of string► In two-dimensional arrays,the first row stores the first string, the second row stores the second string.► For example:-char names[4] [12];
  • Safe operations► As we discuss before, string functions are not safe in general since the size of the string is not controlled(everything depend upon the occurance of the null character)
  • Safe operations►A solution is used in the safer functions:► Strcmp(), strcat(), strcpy()► strcmp(dest ,src,n): compare at mast n character of dest► Strcat(dest ,src,n): concatenate atmost n character of scr to dest► Strcpy(dest, scr, n):copy at most n character of scr to dest
  • String processing► Sscanf() is very similar to scanf(). The only difference is that it takes the the input from a string rather than the console.► Sscanf(char*s, const char,* format,……..)► For eg: char input-str[50];► Int i; float f; char st[10];
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