filter out in C++

[c noob]

letter: upper or lower case a through z
vowel: the letters a, e, i, o or u
consonant: letters that are not vowels
word: a sequence of sequential letters and/or numbers separated by punct or space
number: zero through 9
space: whitespace characters such as space, tab, or newline
punct: punctuation marks such as quote, comma, period, etc.
upper: uppercase letter, vowel, consonant or word
lower: lowercase letter, vowel, consonant or word
The user is going to provide the name of a file and one or more of the items in the list above.

I am having trouble to telling the program that I want it to do that only a specific action and not do all of the actions something like if and else. This is what I have so far.

#include <iostream>
#include <string>
#include <cstring>
#include <fstream>
using namespace std;
int check_vowel(char);
int check_constant(char);
int check_number(char);
int check_punctuation(char);
void usage(char *progname, string msg)
{
    cerr << "Error: " << msg << endl;
    cerr << "Usage is: " << progname << " [filename]" << endl;
    cerr << " specifying filename reads from that file; no filename reads standard input" << endl;
}
int main(int argc, char *argv[])
{
    istream *br;
    ifstream infile;
    
    if( argc == 1 )
        br = &cin;
    else if( argc == 2 ) {
        infile.open(argv[1]);
        if( infile.is_open() )
            br = &infile;
        else {
            usage(argv[0], "Cannot open " + string(argv[1]));
            return 1;
        }
    }
    else {
        usage(argv[0], "More than one file name was given");
        return 1;
    }
    
    string oneLine;
    
    getline(*br, oneLine);
    if( br->good() )
        cout << oneLine << endl;
    else
        cout << "!!! I COULD NOT READ !!!\n";
    
    
    char line[1000];
    
    while( cin.good() ) {
        cin.get(line, 1000, '\n');
        
        cout << line << ":" << strlen(line) << endl;
    }
    

    char v[100], l[100];
    int i, j = 0;
    
    gets(v);
    
    for(i = 0; v[i] != '\0'; i++) {
        if(check_vowel(v[i]) == 0) {       //not a vowel
            l[j] = v[i];
            j++;
        }
    }
    
    l[j] = '\0';
    
    strcpy(v, l);    //We are changing initial string
    
    cout << ("String after deleting vowels: ") << v;
    
    char c[100], t[100];
    int a, b = 0;
    
    gets(c);
    
    for(a = 0; c[a] != '\0'; a++) {
        if(check_vowel(c[a]) == 0) {       //not a vowel
            l[b] = c[a];
            b++;
        }
    }
    
    t[b] = '\0';
    
    strcpy(c, t);    //We are changing initial string
    
    cout << ("String after deleting constants: ") << c;
    
    
    char n[100], r[100];
    int d, f = 0;
    
    gets(n);
    
    for(d = 0; n[d] != '\0'; d++) {
        if(check_number(n[d]) == 0) {       //not a number
            r[f] = n[d];
            f++;
        }
    }
    
    r[f] = '\0';
    
    strcpy(n, r);    //We are changing initial string
    
    cout << ("String after deleting numbers: ") << n << endl;
    
    char p[100], u[100];
    int g, h = 0;
    
    gets(p);
    
    for(g = 0; p[g] != '\0'; g++) {
        if(check_punctuation(p[g]) == 0) {       //not a punctuation
            u[h] = p[g];
            h++;
        }
    }
    
    u[h] = '\0';
    
    strcpy(p, u);    //We are changing initial string
    
    cout << ("String after deleting punctuation: ") << p << endl;

    
    return 0;
}
int check_vowel(char c)
{
    switch(c) {
        case 'a':
        case 'A':
        case 'e':
        case 'E':
        case 'i':
        case 'I':
        case 'o':
        case 'O':
        case 'u':
        case 'U':
            return 1;
        default:
            return 0;
    }
}
    int check_constant(char c)
    {
        switch(c) {
            case 'q':
            case 'w':
            case 'r':
            case 't':
            case 'y':
            case 'i':
            case 'p':
            case 's':
            case 'd':
            case 'f':
            case 'g':
            case 'h':
            case 'j':
            case 'k':
            case 'l':
            case 'z':
            case 'x':
            case 'c':
            case 'v':
            case 'b':
            case 'n':
            case 'm':
            case 'Q':
            case 'W':
            case 'R':
            case 'T':
            case 'Y':
            case 'U':
            case 'P':
            case 'S':
            case 'D':
            case 'F':
            case 'G':
            case 'H':
            case 'J':
            case 'K':
            case 'L':
            case 'Z':
            case 'X':
            case 'C':
            case 'V':
            case 'B':
            case 'N':
            case 'M':
                return 1;
            default:
                return 0;
        }

}
int check_number(char c)
{
    switch(c) {
        case '1':
        case '2':
        case '3':
        case '4':
        case '5':
        case '6':
        case '7':
        case '8':
        case '9':
        case '0':
            return 1;
        default:
            return 0;
    }
}
int check_punctuation(char c)
{
    switch(c) {
        case '.':
        case '?':
        case '!':
        case '"':
        case ',':
        case ';':
        case ':':
            return 1;
        default:
            return 0;
    }
}