Как лучше это сделать? Программа азбуки Морзе

Когда вы используете много if's и после одного совпадения вам нужно двигаться дальше, используйте if-else-if ladder, так что если найдено слово "b", то не будут проверяться все остальные условия.

Но лучшим решением здесь является switch case.

Попробуйте что-нибудь подобное в файле yourfor-loop.

switch (str[i])
{
 case 'a':
   printf("\nIt is an a.\n");
   break;

 case 'b':
   printf("\nIt is a b.\n");
   break;

  /* etc. etc. etc.*/

 default:
 //default will work when the input to the switch->here str[i] does not match any case.
   printf("\nNot a character or space!");
   break;
}

Попробуй это:

    for (...)
    {
       char c = str[i];
       unsigned Num;

       /* If c is a letter map it to 0..25 */
       Num = (unsigned)(toupper(c)-'A');
       if (Num<26) //This matches only with letters, as Num is unsigned.
       {
          //Each letter is represented by max four symbols 
          static const char MorseCodes[26][5]= 
          {
             "._",   //Morsecode for 'a'
             "_...", //Morsecode for 'b'
          ...
             "__..", //Morsecode for 'z'
          };
          printf("You have entered the letter %c. The morse code is %s\n", Num+'A', MorseCodes[Num]);
       }
       else 
       if (c=='_')
       {
          printf ("Space\n");
       } 
       else 
       {
          printf ("What You Are Doing?\n");
       } 
    }

учитывая ваш вопрос, следующий код должен привести вас в правильном направлении.

Обратите внимание, что function: out(), function: delay(), #define ON и #define OFF зависят от вашей среды.

include<stdio.h>
//include<conio.h> -- dont include header files that are not used
include<string.h>

// adjust DELAY_UNIT as necessary
#define DELAY_UNIT (1000)
#define DOT_TIME   (1)
#define DASH_TIME  (3)
#define INTER_WORD_TIME (7)
#define INTER_CHAR_TIME (3)
#define DOT        ('.')
#define DASH       ('-')

// OP needs to define function 'out()', LED, ON, OFF and DELAY_UNIT
// to suit the environment

// prototypes
char *findIndex( struct morseStruct *morse, char ch);
void MorseToLed( char *sequencePtr);
void delay( long unsigned int );

/*
 * If the duration of a dot is taken to be one unit
 * then that of a dash is three units.
 *
 * The space between the components of one character is one unit,
 *
 * between characters is three units and between words seven units.
 *
 * To indicate that a mistake has been made and for the receiver to delete the last word,
 * send ........ (eight dots).
 */

// see <http://morsecode.scphillips.com/morse2.html> for source list
// of morse code char formats

struct morseStruct
{
    char  searchChar;
    char *morseSequence;
};

static const struct morseStruct *alphanumeric[] =
{
    {'A', ",-"   };
    {'B', "-..." };
    {'C', "-.-." };
    ...  // add other alphameric definitions here
    {0, NULL};
};

static const struct morseStruct *punctuation[] =
{
    {'.', ".-.-.-" }; // period
    {',', "--..--" }; // comma
    {':', "---..." }; // colon
    {'?', "..--.." }; // question mark
    {'\'', ".----."}; // apostrophe (note: must escape certain characters)
    {'-', "-....-" }; // hyphen
    {'/', "-..-."  }; // right slash
    {'\"', ".-..-."}; // quotation mark
    {'@', ".--.-." }; // at sign
    {'=', "-...-"  }; // equals sign
    {0, NULL};
};

static const struct morseStruct *prosigns[] =
{
    ... // add prosigns here
    {0, NULL};
};



int main( void )
{

    char str[500];

    printf("Enter a string you want in Morse Code with underscores as spaces: ");
    if( NULL == fgets(str, sizeof( str ), stdin );
    { // then fgets failed
        perror( "fgets for user input string failed");
        exit( EXIT_FAILURE );
    }

    // implied else, fgets successful

    //eliminate trailing newline, if any
    if( char *pNewline = strstr( str, "\n")
    {
        pNewline = '\n';
    }

    size_t stringLength = strlen(str);
    int i;

    for (i = 0; i < stringLength; i++)
    {
        printf("\n[%c]\n", str[i]);


        // handle special cases
        if '_' == str[i] )
        { // then between words
            //out(LED, OFF); // should already be OFF
            delay( INTER_WORD_TIME*DELAY_UNIT );
            continue;
        }

        int sequencePtr;

        if( NULL == (sequencePtr = findIndex( alphaNumeric, str[i] ) ) )
        {// then not alphanumeric value
            if( NULL == (sequencePtr = findIndex( punctuation, str[i] ) ) )
            { // then not punctuation value
                if( NULL == (sequencePtr = findIndex( prosigns, str[i] ) ) )
                { // then not prosign value
                    printf( "char: %0X is not recognized\n", str[i]);
                    continue;
                }
            }
        }

        MorseToLed (sequencePtr);
    } // end for

    return 0;
} // end function: main


char *findIndex( struct morseStruct *morse, char ch)
{
    char *pSequence = NULL;
    int  i = 0;

    while( NULL != morse[i].morseSequence )
    {
        if( ch == morse[i].searchChar )
        { // then found desire morse code sequence
            pSequence = morse[i].morseSequence;
            break;
        }
        i++;
    }
    return( pSequence );
} // end function: findIndex


void MorseToLed( char *sequencePtr)
{
    size_t i = strlen( sequencePtr );

    for( size_t j = 0; j<i; j++)
    {
        if( DOT == sequencePtr[j] )
        {
            out(LED, ON);
            delay( DOT_TIME * DELAY_UNIT );
            out(LED, OFF);
        }
        else if( DASH == sequencePtr[j] )
        {
            out(LED, ON);
            delay( DASH_TIME * DELAY_UNIT );
            out(LED, OFF);
        }
        delay( DELAY_UNIT ); // delay between components of one char
    } // end for

    delay( INTER_CHAR_TIME * DELAY_UNIT ); // delay between characters
} // end function: MorseToLed


void delay( long unsigned int delayUnits )
{
    ?????
} // end function: delay