Difference between const char *p, char * const p and const ...

1. const char *ptr : This is a pointer to a constant character. You cannot change the value pointed by ptr, but you can change the pointer ... 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ImproveArticle SaveArticle LikeArticle DifficultyLevel: EasyLastUpdated: 11Sep,2021Prerequisite:Pointers Thereisalotofconfusionwhenchar,const,*,pareallusedindifferentpermutationsandmeaningschangeaccordingtowhichisplacedwhere.Followingarticlefocusondifferentiationandusageofallofthese. Thequalifierconstcanbeappliedtothedeclarationofanyvariabletospecifythatitsvaluewillnotbechanged.constkeywordappliestowhateverisimmediatelytoitsleft.Ifthereisnothingtoitsleft,itappliestowhateverisimmediatelytoitsright. 1.constchar*ptr:Thisisapointertoaconstantcharacter.Youcannotchangethevaluepointedbyptr,butyoucanchangethepointeritself.“constchar*”isa(non-const)pointertoaconstchar.C//Cprogramtoillustrate//charconst*p#include#include intmain(){    chara='A',b='B';    constchar*ptr=&a;         //*ptr=b;illegalstatement(assignmentofread-onlylocation*ptr)         //ptrcanbechanged    printf("valuepointedtobyptr:%c\n",*ptr);    ptr=&b;    printf("valuepointedtobyptr:%c\n",*ptr);}Output: valuepointedtobyptr:A valuepointedtobyptr:BNOTE:Thereisnodifferencebetweenconstchar*pandcharconst*pasbotharepointertoaconstcharandpositionof‘*'(asterik)isalsosame.  2.char*constptr:Thisisaconstantpointertonon-constantcharacter.Youcannotchangethepointerp,butcanchangethevaluepointedbyptr. C//Cprogramtoillustrate//char*constp#include#include intmain(){    chara='A',b='B';    char*constptr=&a;    printf("Valuepointedtobyptr:%c\n",*ptr);    printf("Addressptrispointingto:%d\n\n",ptr);     //ptr=&b;illegalstatement(assignmentofread-onlyvariableptr)     //changingthevalueattheaddressptrispointingto    *ptr=b;    printf("Valuepointedtobyptr:%c\n",*ptr);    printf("Addressptrispointingto:%d\n",ptr);}Output: Valuepointedtobyptr:A Addressptrispointingto:-1443150762 Valuepointedtobyptr:B Addressptrispointingto:-1443150762NOTE:Pointeralwayspointstosameaddress,onlythevalueatthelocationischanged. 3.constchar*constptr:Thisisaconstantpointertoconstantcharacter.Youcanneitherchangethevaluepointedbyptrnorthepointerptr. C//Cprogramtoillustrate//constchar*constptr#include#include intmain(){    chara='A',b='B';    constchar*constptr=&a;         printf("Valuepointedtobyptr:%c\n",*ptr);    printf("Addressptrispointingto:%d\n\n",ptr);     //ptr=&b;illegalstatement(assignmentofread-onlyvariableptr)    //*ptr=b;illegalstatement(assignmentofread-onlylocation*ptr) }Output: Valuepointedtobyptr:A Addressptrispointingto:-255095482NOTE:charconst*constptrissameasconstchar*constptr. QuizonconstkeywordThisarticleiscontributedbyYashSingla.IfyoulikeGeeksforGeeksandwouldliketocontribute,youcanalsowriteanarticleusingwrite.geeksforgeeks.orgormailyourarticletoreview-team@geeksforgeeks.org.SeeyourarticleappearingontheGeeksforGeeksmainpageandhelpotherGeeks.Pleasewritecommentsifyoufindanythingincorrect,oryouwanttosharemoreinformationaboutthetopicdiscussedabove. MyPersonalNotes arrow_drop_upSave LikeNext PointertoanArray|ArrayPointerRecommendedArticlesPage:19,Dec1807,Aug1416,Nov1529,Jul1415,Oct1906,Sep1726,Nov1002,Oct1203,Oct1122,Sep1327,Aug1328,Aug1330,Aug1305,Feb1430,Jul1405,Sep1825,Oct1803,Apr2018,Aug2002,Feb2131,May1405,Oct1821,May1706,Jan21ArticleContributedBy:GeeksforGeeksVotefordifficultyCurrentdifficulty: EasyEasy Normal Medium Hard ExpertImprovedBy:DeepankarMullickadnanirshad158ArticleTags:C-PointerBasicscpp-pointerCLanguageC++PracticeTags:CPPReportIssueWritingcodeincomment? 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