Add Day 9: Intro to arrays

Author: sahilbansal17

Diff for: Day 9/README.md

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+## Programs for Day 9
+1. [Understanding object and value contexts](pointers1.c)
+2. [Introduction to arrays](arrays.c)
+3. [Array Initialization](arrayInitialization.c)
+4. [Character Array](charArray.c)

Diff for: Day 9/arrayInitialization.c

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+/*
+ * An introduction to array
+ */
+
+#include <stdio.h>
+
+int main () {
+
+	// in the statement below, 5 is an initializer
+	int ordinaryVariable = 5;
+
+	// in the statement below, {1, 2, 3, 4, 5} is an
+	// initializer list
+	int n[5] = {1, 2, 3, 4, 5};
+
+	for (int i = 0; i < 5; i ++) {
+		printf("%d ", n[i]);
+	}
+	printf("\n");
+
+	// less elements in initializer list
+	int a[5] = {1, 2, 3};
+	for (int i = 0; i < 5; i ++) {
+		printf("%d ", a[i]);
+	}
+	printf("\n");
+
+	// we can omit the size if we know the complete initializer list
+	int c[] = {1, 2, 3};
+	for (int i = 0; i < 3; i ++) {
+		printf("%d ", c[i]);
+	}
+	printf("\n");
+	
+	return 0;
+}

Diff for: Day 9/arrays.c

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+/*
+ * An introduction to arrays
+ * Reverse 10 numbers entered by the user
+ */
+
+#include <stdio.h>
+
+int main () {
+
+	// array declaration, 10 integers which are collectively
+	// referred by the variable n
+	int n[10];
+
+	// the indexes start from 0 and till (size-1)
+	for (int i = 0; i < 10; i ++) {
+		scanf("%d", &n[i]);
+	}
+
+	for (int i = 9; i >= 0; i --) {
+		printf("%d ", n[i]);
+	}
+
+	return 0;
+}

Diff for: Day 9/charArray.c

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+/*
+ * Example of character array
+ */
+
+#include <stdio.h>
+
+int main () {
+
+	// specifically, null character '\0'
+	// is required at the end of character array in C
+	
+	/*
+		char name[] = {'K', 'y', 'a', 'm', 'a', ' ', 'P', 'a', 'v', 'a', 'n', 'k', 'a', 'l', 'y', 'a', 'n', '\0'};
+	*/
+	
+	char name[] = "Kyama Pavankalyan";
+	// print the first letter of the name
+	printf("%c\n", name[0]);
+
+	// print the entire name
+	printf("%s\n", name);
+	return 0;
+}

Diff for: Day 9/pointers1.c

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+/*
+ * lvalue expression is the one that is one the left hand side
+ * of an assignment operation
+ * two contexts: value context and object context
+ * value context: the expression is evaluated
+ * object context: we get to the memory location where the object is stored
+ * lvalue expression are in object context
+ */
+
+#include <stdio.h>
+
+int main () {
+
+	// integer declaration
+	// whenever we declare a variable, it gets some memory location	
+	int x, y;
+
+	// &x => x is an object context
+	// we get the location where x resides in the memory
+	// using the & operator
+	// but the &x as an entire expression is in value context
+	y = &x;
+
+	// y will now store the address of the variable x
+
+	printf("%d", y);
+	return 0;
+}