KwickClips C++

C++: 28 short revision clips

One idea per clip, with the answer written out underneath. Each clip links back to the full C++ lesson it came from.

C code int m[3] = {72, 85, 64}; printf m[0], output 72.

What is the first index?43 sec

C code summing array {40, 35, 25} with a for loop, output 100.

Where does i start?40 sec

Grid of a 2D array: row 0 holds 1 and 2, row 1 holds 4 and 5.

Which comes first, row or column?43 sec

Slide: parameter int a[], pass the size separately, changes reach the original.

Is the array copied?41 sec $Table: indexes 0 to 3 hold R, i, y, a; index 4 holds \0.$ What marks the end of a C string?41 sec

Table: scanf %s reads one word, fgets reads full line.

Why did only Riya print?44 sec

Table: strlen length, strcpy copy, strcat join, strcmp compare.

Which header do they need?46 sec

C code while (s[n]) n++; for "Surat", output 5.

Why does while (s[n]) stop?42 sec

Memory boxes: marks at 1000 holds 85, p at 2000 holds 1000.

What does &marks give?41 sec

C code int m = 85; int *p = &m; *p = 90; printf m, output 90.

What does int *p declare?42 sec

Table: p at 1000 holds 10, p + 1 at 1004 holds 20, p + 2 at 1008 holds 30.

How far does p + 1 jump for an int?43 sec

Slide: a[i] equals *(a + i), array name is the first address, pass &x to change x.

What is a[i] the same as?44 sec

Table comparing stack and heap: holds, freed by, size.

Who frees heap memory?43 sec

Table comparing malloc and calloc: arguments, starting values, failure.

Which one gives zeros?43 sec

Slide: realloc keeps old values, save result in a new pointer, free each block once.

Why use a new pointer for realloc?42 sec

Slide: malloc a block, return without free, address lost and block stuck.

Does a leak give an error?40 sec

C code struct st with int roll and float marks, then struct st s = {12, 88.5};

Where is the semicolon needed?41 sec

Table: variable uses dot s.marks, pointer uses arrow p->marks, array uses c[1].roll.

When do you use -›?40 sec

Table comparing structure and union: memory, size, valid values.

What is the size of a union?44 sec

C code enum d { MON, TUE, WED }; printf WED, output 2.

Where does enum counting start?41 sec

Code lines: FILE *fp; fp = fopen("m.txt", "w"); fclose(fp);

What two things does fopen need?43 sec

Table of file functions: character fputc fgetc, line fputs fgets, formatted fprintf fscanf.

Which writes formatted data to a file?44 sec

Table: r read kept, w write erased, a append kept.

Which mode erases the file?40 sec

C code FILE *f = fopen("x.txt", "r"); if (f == NULL) printf Cannot open; else fclose(f);

What does fopen return for a missing file?40 sec

Slide: handles lines starting with #, pastes header files, replaces macros and drops comments.

What runs first, preprocessor or compiler?41 sec

Table: #include pastes a file <stdio.h>, #define names a value PI 3.14.

Should #define end with a semicolon?42 sec

C code #define SQ(x) x * x and printf SQ(2+3), output 11.

What should SQ be?41 sec

Slide: #ifdef DEBUG keep if defined, #if MARKS >= 33 keep if true, #endif closes the block.

When is code kept or dropped?43 sec

Full C++ lessons All KwickClips

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C++: 28 short revision clips

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