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education/computer engineering/ECE1400/Chapter 13 Exercises.md

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+> **1.** The following function calls supposedly write a single new-line character, but some are incorrect. Identify which calls don't work and explain why.
+
+b. `printf("%c", "\n");` - This is invalid because the double quotes make `\n` a string, but it's being displayed with the `%c`formatting specifier.
+c. `printf(%s, '\n');` - This is invalid because it's trying to display a `char` using the string formatting specifier.
+e. `printf('\n');` - `printf`'s first argument should be a string, not a `char`.
+h. `putchar("\n");` - `putchar`'s first argument should be a `char`, not a string.
+i. `puts('\n');` - `puts`'s first argument should be a string, not a `char`.
+j. `puts("\n");` - `puts` will write a newline after writing a string, so this will write two newlines. 
+
+---
+
+> **2.** Suppose that `p` has been declared as follows:
+```c
+char *p = "abc";
+```
+> Which of the following function calls are legal? Show the output produced by each legal call, and explain why all the others are illegal.
+```c
+// A - Not legal, because putchar accepts a `char`, not a pointer.
+putchar(p);
+// B - Legal, output: `a`
+putchar(*p);
+// C - Legal, output: `abc`
+puts(p)
+// D - Illegal, `puts` accepts a pointer to a null terminated string, not a `char`.
+```
+
+---
+
+> **3.** Suppose that we call `scanf` as follows:
+```c
+scanf("%d%s%d", &i, s, &j);
+```
+> If the user enters `12abc34` `56def78`, what will be the values of `i`, `s`, and `j` after the call? (Assume that `i` and `j` are `int` variables and `s` is an array of characters.)
+
+- `i`: `12`
+- `s`: `"abc34"`
+- `j`: `56`
+
+---
+
+> **7.** Suppose that `str` is an array of three characters. Which one of the following statements is not equivalent to the other three?
+```c
+// A
+*str = 0;
+// B
+str[0] = '\0';
+// C
+strcpy(str, "");
+// D
+strcat(str, "");
+```
+(d) is different because it effectively does nothing (concatenates `"abc"` with an empty string). The rest of them make `str` effectively empty by setting the first character to a null byte.
+
+---
+
+> **9.** What will be the value of the string `s1` after the following statements have been executed?
+```c
+// Assuming `str` is an empty string with enough space to store everything:
+strcpy(str, "tire-bouchon");
+// "tire-bouchon"
+strcpy(&str[4], "d-or-wi");
+// "tired-or-wir"
+strcat(str, "red?");
+// "tired-or-wired?"
+```
+
+Expected output:
+```c
+"tired-or-wired?"
+```