Update README.md

Author: jfullstackdev

README.md

@@ -1133,3 +1133,234 @@ using only the memory address of an array.
 ``` 
 
 So, pointers are truly essential to be an excellent C programmer.
+
+# STRUCTURE IN C
+## Source Code
+
+```
+#include <stdio.h>
+
+typedef struct
+{
+   char *name;
+   int age;
+   float height;
+   float grades[10];
+} student;
+
+void printStruct( student oneStudent )
+{
+   int i;
+
+   printf("=====================\n");
+   printf("Student name: %s\n", oneStudent.name);
+   printf("        age: %d\n", oneStudent.age);
+   printf("        height: %6.3f\n", oneStudent.height);
+   printf("        grades: ");
+   for (i=0; i<10; i++) printf("%4.1f ", oneStudent.grades[i]);
+   printf("\n");
+   printf("=====================\n");
+
+}
+
+void modifyStruct( student *oneStudent )
+{
+ 
+   oneStudent->grades[0] = 72.0;
+   oneStudent->grades[4] = 81.0;
+   oneStudent->grades[6] = 85.0;
+
+}
+
+int main()
+{
+
+   student Nikki;
+   Nikki.name = "Nikki";
+   Nikki.age = 19;
+   Nikki.height = 64.75;
+   int i;
+   for (i=0; i<10; i++) {
+      Nikki.grades[i] = 98.0;
+   }
+
+   printStruct(Nikki);
+
+   modifyStruct(&Nikki);
+
+   printStruct(Nikki);
+
+   return 0;
+}
+```
+
+***
+## Result
+
+![result](result.png)
+
+***
+
+## Details
+### Structure Data Type
+This is an example of 
+a structure in C:
+
+```
+typedef struct
+{
+   char *name;
+   int age;
+   float height;
+   float grades[10];
+} student;
+```
+
+where `int age` is in years,
+`float height` in inches
+and `float grades[10]` are the grades 
+for the 10 assignments.
+
+Structure is a user-defined 
+data type in C. It is really needed to
+mix different data types in one declaration.
+
+#### typedef 
+`typedef` is a keyword which will enable
+you to give an existing type a new name. 
+In our case here, it is just like saying:
+"Let us define this structure by 
+calling `student`."
+
+#### Structure Variable
+`student` is a structure
+variable that can access the members of
+this structure.
+
+#### Member Access Operator
+In order to access a member of an
+structure we use `.` symbol, just like
+`oneStudent.name`.
+ 
+***
+A function to print the details:
+
+```
+void printStruct( student oneStudent )
+{
+   int i;
+
+   printf("=====================\n");
+   printf("Student name: %s\n", oneStudent.name);
+   printf("        age: %d\n", oneStudent.age);
+   printf("        height: %6.3f\n", oneStudent.height);
+   printf("        grades: ");
+   for (i=0; i<10; i++) printf("%4.1f ", oneStudent.grades[i]);
+   printf("\n");
+   printf("=====================\n");
+
+}
+```
+
+Take note of this parameter: `student oneStudent`.
+`oneStudent` is a variable of type `student`.
+That is the type we defined in the structure.
+
+Again, you might be overwhelmed by the `printf` function that
+contains strange things like this: `%6.3f`.
+Don't worry, they are just formatting commands like
+whether how many decimal places should be there, or 
+you want to pad those numbers with zero.
+
+In the case of `%6.3f`, it means, format the floating 
+type number 6 digit wide, 3 decimal places.
+
+***
+A function to modify the structure:
+
+```
+void modifyStruct( student *oneStudent )
+{
+   
+   oneStudent->grades[0] = 72.0;
+   oneStudent->grades[4] = 81.0;
+   oneStudent->grades[6] = 85.0;
+
+}
+```
+
+In order to modify the declared structure, 
+we still use pointer as parameter
+to accept a memory location as argument:
+that is, to easily locate it and
+modify everything using the index of each
+data member.
+
+Pointers to structs have special `->` symbol
+for dereferencing the pointer and accessing a 
+data member.
+
+And what does it do?
+`oneStudent->grades[0] = 72.0` is equivalent to
+`(*oneStudent).grades[0] = 72.0`.
+
+***
+In main function, `student`
+data type is used: `student Nikki`
+is just like any other variable
+declaration, like `int myInteger`.
+Coming from the structure we defined,
+we can put data in `student Nikki`.
+
+```
+   student Nikki;
+   Nikki.name = "Nikki";
+   Nikki.age = 19;
+   Nikki.height = 64.75;
+   int i;
+   for (i=0; i<10 ; i++) {
+      Nikki.grades[i] = 98.0;
+   }
+```
+
+The functions we created, we call them in main function
+to act upon the structure:
+
+```
+   printStruct(Nikki);
+
+   modifyStruct(&Nikki);
+
+   printStruct(Nikki);
+```
+
+We first check whether `Nikki` was successfully created by
+calling the command `printStruct(Nikki)`. 
+Then, we modify the initial contents of this structure
+by calling the command `modifyStruct(&Nikki)`. Remember that placing `&`
+before a variable will return the address of that variable.
+And finally, we check again whether the changes were
+saved by calling the command `printStruct(Nikki)`.
+ 
+***
+There are confusing terms that you might be thinking:
+data type, database and data structure.
+
+As was demonstrated, a structure in C is there
+to mix different data types in one declaration. Every member
+can be accessed easily. In general, **data structure** is data that
+can be accessed piece by piece. For example, an XML file is
+considered semi-structured, for elements can be parsed but from
+top to bottom while a database file is a structured data,
+for pieces of information can be accessed randomly without parsing
+the entire database.
+
+**Data type** is declared to easily tell the compiler
+how a particular data should be treated. 
+
+**Database** is an organized
+collection of data usually expressed as tables.
+It is commonly built upon a filesystem.
+Data will persist after the computer is turned off because data
+resides on persistent storage.
+