Arguments and pointers

01-arguments.c

@@ -0,0 +1,12 @@
+#include <stdio.h>
+
+int main(int argc, char** argv) {
+    printf("Given %d arguments.\n", argc);
+
+    int index = 0;
+    while (index < argc) {
+        printf("Argument %d: %s\n", index, argv[index]);
+        index = index + 1;
+    }
+}
+

README.md

@@ -143,7 +143,65 @@ printf("Hello, world!\n");
 ```
 
 This calls the `printf` function, which `print`s a `f`ormatted string, although we're
-not using any of the formatting options here.
+not using any of the formatting options here. The `\n` is a standin for the newline
+character.
 
-Congratulations! This is your first C program~
+Congratulations! This is your first C program, and demonstrates that your development
+environment is working.
 
+# Pointers and Looping
+
+In a file called `01-arguments.c`, write:
+
+```c
+#include <stdio.h>
+
+int main(int argc, char** argv) {
+    printf("Given %d arguments.\n", argc);
+
+    int index = 0;
+    while (index < argc) {
+        printf("Argument %d: %s\n", index, argv[index]);
+        index = index + 1;
+    }
+}
+```
+
+This is pretty similar, but has a few more complications.
+
+```c
+printf("Given %d arguments.\n", argc);
+```
+
+Here, `%d` means "replace this placeholder with the first argument after the string,
+which should be an integer". `d` stands for digit.
+
+```c
+int index = 0;
+```
+
+This is the declaration of a variable "index", which will be used to keep track of our
+place in the array.
+
+```c
+while (index < argc) {
+```
+
+This means run the following code until the `index` variable becomes greater than or equal
+to `argc`, the number of command line arguments.
+
+```c
+printf("Argument %d: %s\n", index, argv[index]);
+```
+
+This line has a few new things in it; `%s` is the placeholder for strings, and `argv[index]`
+is taking looking at the `index`th element in `argv`, an array of strings.
+
+Or, you can look at it a different way: `argv` is a `char**`, a `*` (pointer) to a `*` (pointer)
+to a `char`. A "pointer" is simply an **unsigned integer** which represents, instead of a
+number, a location in memory.
+
+So, `char** argv` is the memory location of the first element in a list of pointers, each
+of which is the memory location of the first element in a list of `char`s. Those lists of
+`char`s all end with `\0`, the 0 byte, and represent the text of the program's command
+line arguments.