String

The string data-type is an ordered collection of characters. The length of a string variable is the number of characters in the collection which can have dynamic length and vary during the course of a simulation. A string variable does not represent a string in the same way as a string literal. No truncation occurs when using the string variable. 

variable_name is a valid identifier and the optional initial_value can be a string literal, the value "" for an empty string, or a string data type expression. If an initial value is not specified at the time of declaration, then the variable defaults to "", an empty string literal. 

A single ASCII character requires 8-bits (1 byte) and to store a string we would need as many bytes as there are number of characters in the string. 

module string_data_type;

  reg [0:15*8-1]s;

  string s0;

  bit[31:0]b;

  initial begin

    s = "how are you doing";//17chars

    $display("String s = %0s",s);

    s = "Hello World";//11chars

    $display("String s = %0s",s);

  //s0-> empty string

    $display("String s0 = %0s",s0);

    s0 = "Hello World ssssss";//11chars

    $display("String s0 = %0s",s0);

    s0 = string'({"Hi, "," ",s});

    $display("String s0 = %0s",s0);

//      Bug

    b = 128;

    s0 = string'(b); // sets 128 to s0

    $display("s0 = %0s \n bit b = %0d",s0,b);

    $sformat(s0, "%s", b);

    $display("s0 = %0s \n bit b = %0d",s0,b);

    s0="welcome to We_LSI channel,practice at the end of the session \

All the best";

    $display("s0 = %0s",s0);

  end

endmodule

//-------------------------------------------------------

module string_operator;

  string s1="Hi Everyone";//11

  string s2="He Everyone";//11

  string s3;

  initial begin

    if(s1==s2)

         $display("s1=%0s equals to s2=%0s",s1,s2);

    else $display("s1 is not equals to s2");

    if(s1<s2)//<=,>,>=

         $display("s1=%0s is less than s2=%0s",s1,s2);

    else

         $display("s1 is not less than s2");

    s3={s1," welcome ",s2};

    $display("s3=%0s",s3);

    s3={3{"We_LSI"}};             //{5{s1}}

    $display("s3=%0s",s3);

    s3="Hello guys";

    $display("s3=%0d s3=%0s",s3[7],s3[7]);

    end

endmodule

//-------------------------basic methods---------------------------

module string_basic_methods;

  string s1="Hi Everyone";//11

  string s2="He Everyone";//11

  string s3;

  initial begin

    $display("s1=%0d",s1.len());

    s1.putc(2,"char");

    $display("s1=%0s",s1);

    // s1.putc(2,"char")               //s1=Hiceveryone

    $display("s1=%0s=%0d", s1.getc(2), s1.getc(2));

    s1="ENGINEERING";

    $display("s1=%0s",s1.tolower());

    $display("s1=%0s",s1.toupper());

   // s2="ENGINEERING";

    s2="EZgineering";//A=65 a=97

    $display("s1=%0s s2=%0s difference=%0d",s1,s2,s1.compare(s2));

    //(s1-s2)case sensitive(0=equ,neg=s1<s2,pos=s1>s2)

    $display("s1=%0s s2=%0s difference=%0d",s1,s2,s1.icompare(s2)); //case insensitive

  end

endmodule

1. https://www.chipverify.com/systemverilog/systemverilog-strings

2. Book System Verilog for Verification by CHRIS SPEAR