60 lines
2.1 KiB
Markdown
60 lines
2.1 KiB
Markdown
> **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.
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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.
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c. `printf(%s, '\n');` - This is invalid because it's trying to display a `char` using the string formatting specifier.
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e. `printf('\n');` - `printf`'s first argument should be a string, not a `char`.
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h. `putchar("\n");` - `putchar`'s first argument should be a `char`, not a string.
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i. `puts('\n');` - `puts`'s first argument should be a string, not a `char`.
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j. `puts("\n");` - `puts` will write a newline after writing a string, so this will write two newlines.
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---
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> **2.** Suppose that `p` has been declared as follows:
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```c
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char *p = "abc";
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```
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> Which of the following function calls are legal? Show the output produced by each legal call, and explain why all the others are illegal.
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```c
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// A - Not legal, because putchar accepts a `char`, not a pointer.
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putchar(p);
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// B - Legal, output: `a`
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putchar(*p);
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// C - Legal, output: `abc`
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puts(p)
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// D - Illegal, `puts` accepts a pointer to a null terminated string, not a `char`.
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```
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---
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> **3.** Suppose that we call `scanf` as follows:
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```c
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scanf("%d%s%d", &i, s, &j);
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```
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> 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.)
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- `i`: `12`
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- `s`: `"abc34"`
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- `j`: `56`
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---
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> **7.** Suppose that `str` is an array of three characters. Which one of the following statements is not equivalent to the other three?
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```c
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// A
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*str = 0;
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// B
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str[0] = '\0';
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// C
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strcpy(str, "");
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// D
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strcat(str, "");
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```
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(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.
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---
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> **9.** What will be the value of the string `s1` after the following statements have been executed?
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```c
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strcpy(str, "tire-bouchon");
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strcpy(&str[4], "d-or-wi")
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``` |