centralized performance resources

ocw/1/c-primer/pointer.c

@@ -0,0 +1,47 @@
+// Copyright (c) 2012 MIT License by 6.172 Staff
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <stdint.h>
+
+int main(int argc, char * argv[]) {  // What is the type of argv?
+  int i = 5;
+  // The & operator here gets the address of i and stores it into pi
+  int * pi = &i;
+  // The * operator here dereferences pi and stores the value -- 5 --
+  // into j.
+  int j = *pi;
+
+  char c[] = "6.172";
+  char * pc = c;  // Valid assignment: c acts like a pointer to c[0] here.
+  char d = *pc;
+  printf("char d = %c\n", d);  // What does this print?
+
+  // compound types are read right to left in C.
+  // pcp is a pointer to a pointer to a char, meaning that
+  // pcp stores the address of a char pointer.
+  char ** pcp;
+  pcp = argv;  // Why is this assignment valid?
+
+  const char * pcc = c;  // pcc is a pointer to char constant
+  char const * pcc2 = c;  // What is the type of pcc2?
+
+  // For each of the following, why is the assignment:
+  *pcc = '7';  // invalid?
+  pcc = *pcp;  // valid?
+  pcc = argv[0];  // valid?
+
+  char * const cp = c;  // cp is a const pointer to char
+  // For each of the following, why is the assignment:
+  cp = *pcp;  // invalid?
+  cp = *argv;  // invalid?
+  *cp = '!';  // valid?
+
+  const char * const cpc = c;  // cpc is a const pointer to char const
+  // For each of the following, why is the assignment:
+  cpc = *pcp;  // invalid?
+  cpc = argv[0];  // invalid?
+  *cpc = '@';  // invalid?
+
+  return 0;
+}